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	$52.50	10.747%	$58.1422	$58.14	$58.15	$58.10
Purchase #2	$84.85	5.190%	$89.2537	$89.25	$89.25	$89.30
Purchase #3	$62.88	5.410%	$66.2818	$66.28	$66.30	$66.30
Purchase #4	$31.76	11.165%	$35.306	$35.31	$35.30	$35.30
Purchase #5	$47.74	7.138%	$51.1477	$51.15	$51.15	$51.10
Purchase #6	$66.35	8.702%	$72.1238	$72.12	$72.10	$72.10
Purchase #7	$33.95	6.392%	$36.1201	$36.12	$36.10	$36.10
7 purchase totals =	$380.03		$408.3753	$408.37	$408.35	$408.30