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	$143.51	11.819%	$160.4714	$160.47	$160.45	$160.50
Purchase #2	$203.73	9.192%	$222.4569	$222.46	$222.45	$222.50
Purchase #3	$42.50	9.459%	$46.5201	$46.52	$46.50	$46.50
Purchase #4	$160.42	4.512%	$167.6582	$167.66	$167.65	$167.70
Purchase #5	$153.43	7.370%	$164.7378	$164.74	$164.75	$164.70
Purchase #6	$227.90	8.434%	$247.1211	$247.12	$247.10	$247.10
Purchase #7	$47.69	7.475%	$51.2548	$51.25	$51.25	$51.30
7 purchase totals =	$979.18		$1,060.2203	$1,060.22	$1,060.15	$1,060.30