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	$67.62	13.111%	$76.4857	$76.49	$76.50	$76.50
Purchase #2	$110.93	11.432%	$123.6115	$123.61	$123.60	$123.60
Purchase #3	$188.90	10.296%	$208.3491	$208.35	$208.35	$208.30
Purchase #4	$136.33	11.420%	$151.8989	$151.90	$151.90	$151.90
Purchase #5	$168.76	12.354%	$189.6086	$189.61	$189.60	$189.60
Purchase #6	$74.96	8.307%	$81.1869	$81.19	$81.20	$81.20
Purchase #7	$176.64	8.218%	$191.1563	$191.16	$191.15	$191.20
7 purchase totals =	$924.14		$1,022.2970	$1,022.31	$1,022.30	$1,022.30