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	$46.68	8.671%	$50.7276	$50.73	$50.75	$50.70
Purchase #2	$171.68	6.144%	$182.228	$182.23	$182.25	$182.20
Purchase #3	$54.87	13.738%	$62.408	$62.41	$62.40	$62.40
Purchase #4	$241.85	3.605%	$250.5687	$250.57	$250.55	$250.60
Purchase #5	$236.91	10.736%	$262.3447	$262.34	$262.35	$262.30
Purchase #6	$155.76	4.145%	$162.2163	$162.22	$162.20	$162.20
Purchase #7	$31.35	11.288%	$34.8888	$34.89	$34.90	$34.90
7 purchase totals =	$939.10		$1,005.3821	$1,005.39	$1,005.40	$1,005.30