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	$67.62	4.498%	$70.6615	$70.66	$70.65	$70.70
Purchase #2	$187.36	12.812%	$211.3646	$211.36	$211.35	$211.40
Purchase #3	$218.49	10.322%	$241.0425	$241.04	$241.05	$241.00
Purchase #4	$227.60	10.647%	$251.8326	$251.83	$251.85	$251.80
Purchase #5	$111.82	13.780%	$127.2288	$127.23	$127.25	$127.20
Purchase #6	$173.31	4.299%	$180.7606	$180.76	$180.75	$180.80
Purchase #7	$80.95	5.750%	$85.6046	$85.60	$85.60	$85.60
7 purchase totals =	$1,067.15		$1,168.4952	$1,168.48	$1,168.50	$1,168.50