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	$57.95	5.477%	$61.1239	$61.12	$61.10	$61.10
Purchase #2	$248.96	10.346%	$274.7174	$274.72	$274.70	$274.70
Purchase #3	$198.63	5.121%	$208.8018	$208.80	$208.80	$208.80
Purchase #4	$12.59	13.328%	$14.268	$14.27	$14.25	$14.30
Purchase #5	$211.51	5.625%	$223.4074	$223.41	$223.40	$223.40
Purchase #6	$136.66	5.496%	$144.1708	$144.17	$144.15	$144.20
Purchase #7	$96.42	7.271%	$103.4307	$103.43	$103.45	$103.40
7 purchase totals =	$962.72		$1,029.9200	$1,029.92	$1,029.85	$1,029.90