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	$199.81	6.148%	$212.0943	$212.09	$212.10	$212.10
Purchase #2	$96.52	3.314%	$99.7187	$99.72	$99.70	$99.70
Purchase #3	$160.33	9.133%	$174.9729	$174.97	$174.95	$175.00
Purchase #4	$57.38	4.379%	$59.8927	$59.89	$59.90	$59.90
Purchase #5	$66.64	13.729%	$75.789	$75.79	$75.80	$75.80
Purchase #6	$159.90	3.578%	$165.6212	$165.62	$165.60	$165.60
Purchase #7	$98.79	8.144%	$106.8355	$106.84	$106.85	$106.80
7 purchase totals =	$839.37		$894.9243	$894.92	$894.90	$894.90