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	$241.69	13.796%	$275.0336	$275.03	$275.05	$275.00
Purchase #2	$125.87	9.241%	$137.5016	$137.50	$137.50	$137.50
Purchase #3	$214.46	6.132%	$227.6107	$227.61	$227.60	$227.60
Purchase #4	$106.33	5.185%	$111.8432	$111.84	$111.85	$111.80
Purchase #5	$156.30	7.399%	$167.8646	$167.86	$167.85	$167.90
Purchase #6	$41.85	6.787%	$44.6904	$44.69	$44.70	$44.70
Purchase #7	$42.92	4.824%	$44.9905	$44.99	$45.00	$45.00
7 purchase totals =	$929.42		$1,009.5346	$1,009.52	$1,009.55	$1,009.50