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	$212.62	4.155%	$221.4544	$221.45	$221.45	$221.50
Purchase #2	$52.39	10.657%	$57.9732	$57.97	$57.95	$58.00
Purchase #3	$86.33	3.494%	$89.3464	$89.35	$89.35	$89.30
Purchase #4	$112.85	4.759%	$118.2205	$118.22	$118.20	$118.20
Purchase #5	$93.85	13.223%	$106.2598	$106.26	$106.25	$106.30
Purchase #6	$6.99	12.269%	$7.8476	$7.85	$7.85	$7.80
Purchase #7	$54.78	9.129%	$59.7809	$59.78	$59.80	$59.80
7 purchase totals =	$619.81		$660.8828	$660.88	$660.85	$660.90