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	$50.39	6.826%	$53.8296	$53.83	$53.85	$53.80
Purchase #2	$71.59	10.246%	$78.9251	$78.93	$78.95	$78.90
Purchase #3	$39.71	5.430%	$41.8663	$41.87	$41.85	$41.90
Purchase #4	$174.62	11.270%	$194.2997	$194.30	$194.30	$194.30
Purchase #5	$82.33	6.377%	$87.5802	$87.58	$87.60	$87.60
Purchase #6	$183.31	7.355%	$196.7925	$196.79	$196.80	$196.80
Purchase #7	$35.78	6.547%	$38.1225	$38.12	$38.10	$38.10
7 purchase totals =	$637.73		$691.4159	$691.42	$691.45	$691.40