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	$119.34	9.698%	$130.9136	$130.91	$130.90	$130.90
Purchase #2	$78.92	12.850%	$89.0612	$89.06	$89.05	$89.10
Purchase #3	$104.89	3.243%	$108.2916	$108.29	$108.30	$108.30
Purchase #4	$144.33	7.518%	$155.1807	$155.18	$155.20	$155.20
Purchase #5	$145.31	10.606%	$160.7216	$160.72	$160.70	$160.70
Purchase #6	$248.98	5.445%	$262.537	$262.54	$262.55	$262.50
Purchase #7	$93.87	7.557%	$100.9638	$100.96	$100.95	$101.00
7 purchase totals =	$935.64		$1,007.6695	$1,007.66	$1,007.65	$1,007.70