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	$213.37	4.656%	$223.3045	$223.30	$223.30	$223.30
Purchase #2	$47.51	6.343%	$50.5236	$50.52	$50.50	$50.50
Purchase #3	$86.48	3.601%	$89.5941	$89.59	$89.60	$89.60
Purchase #4	$219.76	9.593%	$240.8416	$240.84	$240.85	$240.80
Purchase #5	$159.28	9.802%	$174.8926	$174.89	$174.90	$174.90
Purchase #6	$234.61	7.110%	$251.2908	$251.29	$251.30	$251.30
Purchase #7	$217.74	11.491%	$242.7605	$242.76	$242.75	$242.80
7 purchase totals =	$1,178.75		$1,273.2077	$1,273.19	$1,273.20	$1,273.20