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	$51.59	3.855%	$53.5788	$53.58	$53.60	$53.60
Purchase #2	$71.44	6.755%	$76.2658	$76.27	$76.25	$76.30
Purchase #3	$222.62	11.539%	$248.3081	$248.31	$248.30	$248.30
Purchase #4	$67.87	7.773%	$73.1455	$73.15	$73.15	$73.10
Purchase #5	$61.78	4.219%	$64.3865	$64.39	$64.40	$64.40
Purchase #6	$186.95	13.264%	$211.747	$211.75	$211.75	$211.70
Purchase #7	$91.82	8.489%	$99.6146	$99.61	$99.60	$99.60
7 purchase totals =	$754.07		$827.0463	$827.06	$827.05	$827.00