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	$175.38	3.629%	$181.7445	$181.74	$181.75	$181.70
Purchase #2	$38.86	6.679%	$41.4555	$41.46	$41.45	$41.50
Purchase #3	$118.34	7.872%	$127.6557	$127.66	$127.65	$127.70
Purchase #4	$166.94	13.404%	$189.3166	$189.32	$189.30	$189.30
Purchase #5	$183.73	4.170%	$191.3915	$191.39	$191.40	$191.40
Purchase #6	$70.47	8.626%	$76.5487	$76.55	$76.55	$76.50
Purchase #7	$214.83	9.644%	$235.5482	$235.55	$235.55	$235.50
7 purchase totals =	$968.55		$1,043.6607	$1,043.67	$1,043.65	$1,043.60