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	$109.72	8.517%	$119.0649	$119.06	$119.05	$119.10
Purchase #2	$44.79	8.736%	$48.7029	$48.70	$48.70	$48.70
Purchase #3	$64.79	3.687%	$67.1788	$67.18	$67.20	$67.20
Purchase #4	$69.89	12.489%	$78.6186	$78.62	$78.60	$78.60
Purchase #5	$59.63	3.122%	$61.4916	$61.49	$61.50	$61.50
Purchase #6	$70.85	3.162%	$73.0903	$73.09	$73.10	$73.10
Purchase #7	$113.36	12.112%	$127.0902	$127.09	$127.10	$127.10
7 purchase totals =	$533.03		$575.2373	$575.23	$575.25	$575.30