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	$241.87	9.830%	$265.6458	$265.65	$265.65	$265.60
Purchase #2	$234.49	6.489%	$249.7061	$249.71	$249.70	$249.70
Purchase #3	$195.41	9.234%	$213.4542	$213.45	$213.45	$213.50
Purchase #4	$18.93	6.169%	$20.0978	$20.10	$20.10	$20.10
Purchase #5	$7.40	6.853%	$7.9071	$7.91	$7.90	$7.90
Purchase #6	$169.92	7.738%	$183.0684	$183.07	$183.05	$183.10
Purchase #7	$200.87	10.673%	$222.3089	$222.31	$222.30	$222.30
7 purchase totals =	$1,068.89		$1,162.1883	$1,162.20	$1,162.15	$1,162.20