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	$221.48	11.280%	$246.4629	$246.46	$246.45	$246.50
Purchase #2	$151.41	8.734%	$164.6341	$164.63	$164.65	$164.60
Purchase #3	$55.50	11.658%	$61.9702	$61.97	$61.95	$62.00
Purchase #4	$99.51	3.822%	$103.3133	$103.31	$103.30	$103.30
Purchase #5	$226.83	7.528%	$243.9058	$243.91	$243.90	$243.90
Purchase #6	$158.43	9.586%	$173.6171	$173.62	$173.60	$173.60
Purchase #7	$51.91	9.327%	$56.7516	$56.75	$56.75	$56.80
7 purchase totals =	$965.07		$1,050.6550	$1,050.65	$1,050.60	$1,050.70