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	$191.57	13.418%	$217.2749	$217.27	$217.25	$217.30
Purchase #2	$234.51	12.232%	$263.1953	$263.20	$263.20	$263.20
Purchase #3	$140.69	11.212%	$156.4642	$156.46	$156.45	$156.50
Purchase #4	$149.32	13.555%	$169.5603	$169.56	$169.55	$169.60
Purchase #5	$52.88	9.613%	$57.9634	$57.96	$57.95	$58.00
Purchase #6	$134.85	11.581%	$150.467	$150.47	$150.45	$150.50
Purchase #7	$125.45	4.298%	$130.8418	$130.84	$130.85	$130.80
7 purchase totals =	$1,029.27		$1,145.7669	$1,145.76	$1,145.70	$1,145.90