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	$91.76	8.186%	$99.2715	$99.27	$99.25	$99.30
Purchase #2	$210.91	4.621%	$220.6562	$220.66	$220.65	$220.70
Purchase #3	$133.68	8.112%	$144.5241	$144.52	$144.50	$144.50
Purchase #4	$246.98	3.307%	$255.1476	$255.15	$255.15	$255.10
Purchase #5	$62.70	13.424%	$71.1168	$71.12	$71.10	$71.10
Purchase #6	$248.88	8.350%	$269.6615	$269.66	$269.65	$269.70
Purchase #7	$86.61	10.452%	$95.6625	$95.66	$95.65	$95.70
7 purchase totals =	$1,081.52		$1,156.0402	$1,156.04	$1,155.95	$1,156.10