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	$135.57	5.231%	$142.6617	$142.66	$142.65	$142.70
Purchase #2	$218.28	11.234%	$242.8016	$242.80	$242.80	$242.80
Purchase #3	$249.48	11.170%	$277.3469	$277.35	$277.35	$277.30
Purchase #4	$67.78	11.711%	$75.7177	$75.72	$75.70	$75.70
Purchase #5	$86.70	3.680%	$89.8906	$89.89	$89.90	$89.90
Purchase #6	$226.86	13.230%	$256.8736	$256.87	$256.85	$256.90
Purchase #7	$240.87	9.311%	$263.2974	$263.30	$263.30	$263.30
7 purchase totals =	$1,225.54		$1,348.5895	$1,348.59	$1,348.55	$1,348.60