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	$187.74	9.639%	$205.8363	$205.84	$205.85	$205.80
Purchase #2	$67.75	10.618%	$74.9437	$74.94	$74.95	$74.90
Purchase #3	$53.26	11.587%	$59.4312	$59.43	$59.45	$59.40
Purchase #4	$135.75	4.196%	$141.4461	$141.45	$141.45	$141.40
Purchase #5	$186.56	5.133%	$196.1361	$196.14	$196.15	$196.10
Purchase #6	$229.83	7.612%	$247.3247	$247.32	$247.30	$247.30
Purchase #7	$35.27	11.725%	$39.4054	$39.41	$39.40	$39.40
7 purchase totals =	$896.16		$964.5235	$964.53	$964.55	$964.30