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	$231.60	7.116%	$248.0807	$248.08	$248.10	$248.10
Purchase #2	$126.63	11.451%	$141.1304	$141.13	$141.15	$141.10
Purchase #3	$198.61	12.740%	$223.9129	$223.91	$223.90	$223.90
Purchase #4	$123.57	4.588%	$129.2394	$129.24	$129.25	$129.20
Purchase #5	$151.82	3.285%	$156.8073	$156.81	$156.80	$156.80
Purchase #6	$98.46	4.773%	$103.1595	$103.16	$103.15	$103.20
Purchase #7	$162.73	4.293%	$169.716	$169.72	$169.70	$169.70
7 purchase totals =	$1,093.42		$1,172.0462	$1,172.05	$1,172.05	$1,172.00