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	$127.79	3.673%	$132.4837	$132.48	$132.50	$132.50
Purchase #2	$248.78	11.173%	$276.5762	$276.58	$276.60	$276.60
Purchase #3	$92.51	9.787%	$101.564	$101.56	$101.55	$101.60
Purchase #4	$202.97	11.372%	$226.0517	$226.05	$226.05	$226.10
Purchase #5	$61.83	13.133%	$69.9501	$69.95	$69.95	$70.00
Purchase #6	$144.51	4.595%	$151.1502	$151.15	$151.15	$151.20
Purchase #7	$85.44	4.847%	$89.5813	$89.58	$89.60	$89.60
7 purchase totals =	$963.83		$1,047.3572	$1,047.35	$1,047.40	$1,047.60