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	$39.68	11.263%	$44.1492	$44.15	$44.15	$44.10
Purchase #2	$130.97	11.198%	$145.636	$145.64	$145.65	$145.60
Purchase #3	$216.82	13.223%	$245.4901	$245.49	$245.50	$245.50
Purchase #4	$107.88	7.108%	$115.5481	$115.55	$115.55	$115.50
Purchase #5	$50.45	3.785%	$52.3595	$52.36	$52.35	$52.40
Purchase #6	$134.83	6.247%	$143.2528	$143.25	$143.25	$143.30
Purchase #7	$242.63	5.486%	$255.9407	$255.94	$255.95	$255.90
7 purchase totals =	$923.26		$1,002.3764	$1,002.38	$1,002.40	$1,002.30