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	$234.54	3.740%	$243.3118	$243.31	$243.30	$243.30
Purchase #2	$246.32	4.298%	$256.9068	$256.91	$256.90	$256.90
Purchase #3	$83.72	12.343%	$94.0536	$94.05	$94.05	$94.10
Purchase #4	$90.53	4.140%	$94.2779	$94.28	$94.30	$94.30
Purchase #5	$145.60	9.115%	$158.8714	$158.87	$158.85	$158.90
Purchase #6	$59.37	6.807%	$63.4113	$63.41	$63.40	$63.40
Purchase #7	$224.29	3.148%	$231.3506	$231.35	$231.35	$231.40
7 purchase totals =	$1,084.37		$1,142.1834	$1,142.18	$1,142.15	$1,142.30