Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$110.46	11.490%	$123.1519	$123.15	$123.15	$123.20
Purchase #2	$146.61	4.352%	$152.9905	$152.99	$153.00	$153.00
Purchase #3	$230.27	3.645%	$238.6633	$238.66	$238.65	$238.70
Purchase #4	$206.26	9.371%	$225.5886	$225.59	$225.60	$225.60
Purchase #5	$131.35	12.462%	$147.7188	$147.72	$147.70	$147.70
Purchase #6	$171.66	11.333%	$191.1142	$191.11	$191.10	$191.10
Purchase #7	$91.49	13.303%	$103.6609	$103.66	$103.65	$103.70
7 purchase totals =	$1,088.10		$1,182.8882	$1,182.88	$1,182.85	$1,183.00