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	$134.33	6.228%	$142.6961	$142.70	$142.70	$142.70
Purchase #2	$160.98	8.622%	$174.8597	$174.86	$174.85	$174.90
Purchase #3	$186.50	6.357%	$198.3558	$198.36	$198.35	$198.40
Purchase #4	$81.82	9.731%	$89.7819	$89.78	$89.80	$89.80
Purchase #5	$209.44	11.673%	$233.8879	$233.89	$233.90	$233.90
Purchase #6	$218.87	11.756%	$244.6004	$244.60	$244.60	$244.60
Purchase #7	$45.73	10.532%	$50.5463	$50.55	$50.55	$50.50
7 purchase totals =	$1,037.67		$1,134.7281	$1,134.74	$1,134.75	$1,134.80