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	$140.91	8.199%	$152.4632	$152.46	$152.45	$152.50
Purchase #2	$200.62	8.530%	$217.7329	$217.73	$217.75	$217.70
Purchase #3	$33.83	12.846%	$38.1758	$38.18	$38.20	$38.20
Purchase #4	$247.94	6.763%	$264.7082	$264.71	$264.70	$264.70
Purchase #5	$119.89	8.154%	$129.6658	$129.67	$129.65	$129.70
Purchase #6	$181.46	9.549%	$198.7876	$198.79	$198.80	$198.80
Purchase #7	$53.93	10.713%	$59.7075	$59.71	$59.70	$59.70
7 purchase totals =	$978.58		$1,061.2410	$1,061.25	$1,061.25	$1,061.30