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	$60.54	7.225%	$64.914	$64.91	$64.90	$64.90
Purchase #2	$48.64	13.231%	$55.0756	$55.08	$55.10	$55.10
Purchase #3	$127.80	13.718%	$145.3316	$145.33	$145.35	$145.30
Purchase #4	$7.99	4.210%	$8.3264	$8.33	$8.35	$8.30
Purchase #5	$100.80	11.198%	$112.0876	$112.09	$112.10	$112.10
Purchase #6	$79.87	3.685%	$82.8132	$82.81	$82.80	$82.80
Purchase #7	$50.66	11.751%	$56.6131	$56.61	$56.60	$56.60
7 purchase totals =	$476.30		$525.1615	$525.16	$525.20	$525.10