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	$128.46	13.225%	$145.4488	$145.45	$145.45	$145.40
Purchase #2	$88.97	8.362%	$96.4097	$96.41	$96.40	$96.40
Purchase #3	$84.34	9.823%	$92.6247	$92.62	$92.60	$92.60
Purchase #4	$35.46	5.727%	$37.4908	$37.49	$37.50	$37.50
Purchase #5	$159.97	8.828%	$174.0922	$174.09	$174.10	$174.10
Purchase #6	$92.95	4.422%	$97.0602	$97.06	$97.05	$97.10
Purchase #7	$59.71	4.681%	$62.505	$62.51	$62.50	$62.50
7 purchase totals =	$649.86		$705.6314	$705.63	$705.60	$705.60