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	$68.58	4.269%	$71.5077	$71.51	$71.50	$71.50
Purchase #2	$130.33	5.279%	$137.2101	$137.21	$137.20	$137.20
Purchase #3	$18.63	10.398%	$20.5671	$20.57	$20.55	$20.60
Purchase #4	$158.61	8.628%	$172.2949	$172.29	$172.30	$172.30
Purchase #5	$161.72	12.792%	$182.4072	$182.41	$182.40	$182.40
Purchase #6	$104.72	10.179%	$115.3794	$115.38	$115.40	$115.40
Purchase #7	$33.62	4.742%	$35.2143	$35.21	$35.20	$35.20
7 purchase totals =	$676.21		$734.5807	$734.58	$734.55	$734.60