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	$188.38	5.404%	$198.5601	$198.56	$198.55	$198.60
Purchase #2	$231.89	4.590%	$242.5338	$242.53	$242.55	$242.50
Purchase #3	$131.50	13.830%	$149.6865	$149.69	$149.70	$149.70
Purchase #4	$144.36	12.761%	$162.7818	$162.78	$162.80	$162.80
Purchase #5	$37.65	10.485%	$41.5976	$41.60	$41.60	$41.60
Purchase #6	$173.39	7.335%	$186.1082	$186.11	$186.10	$186.10
Purchase #7	$45.95	7.343%	$49.3241	$49.32	$49.30	$49.30
7 purchase totals =	$953.12		$1,030.5921	$1,030.59	$1,030.60	$1,030.60