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	$102.49	6.441%	$109.0914	$109.09	$109.10	$109.10
Purchase #2	$239.92	8.641%	$260.6515	$260.65	$260.65	$260.70
Purchase #3	$52.29	3.781%	$54.2671	$54.27	$54.25	$54.30
Purchase #4	$168.74	9.709%	$185.123	$185.12	$185.10	$185.10
Purchase #5	$29.76	9.795%	$32.675	$32.68	$32.70	$32.70
Purchase #6	$123.51	5.705%	$130.5562	$130.56	$130.55	$130.60
Purchase #7	$238.36	11.134%	$264.899	$264.90	$264.90	$264.90
7 purchase totals =	$955.07		$1,037.2632	$1,037.27	$1,037.25	$1,037.40