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	$62.89	3.602%	$65.1553	$65.16	$65.15	$65.20
Purchase #2	$29.81	8.266%	$32.2741	$32.27	$32.25	$32.30
Purchase #3	$17.43	4.604%	$18.2325	$18.23	$18.25	$18.20
Purchase #4	$82.94	9.439%	$90.7687	$90.77	$90.75	$90.80
Purchase #5	$160.93	8.197%	$174.1214	$174.12	$174.10	$174.10
Purchase #6	$106.58	6.820%	$113.8488	$113.85	$113.85	$113.80
Purchase #7	$108.34	6.859%	$115.771	$115.77	$115.75	$115.80
7 purchase totals =	$568.92		$610.1718	$610.17	$610.10	$610.20