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	$69.62	7.570%	$74.8902	$74.89	$74.90	$74.90
Purchase #2	$148.44	10.505%	$164.0336	$164.03	$164.05	$164.00
Purchase #3	$216.72	13.166%	$245.2534	$245.25	$245.25	$245.30
Purchase #4	$84.42	7.659%	$90.8857	$90.89	$90.90	$90.90
Purchase #5	$79.42	13.392%	$90.0559	$90.06	$90.05	$90.10
Purchase #6	$180.62	12.581%	$203.3438	$203.34	$203.35	$203.30
Purchase #7	$192.76	6.309%	$204.9212	$204.92	$204.90	$204.90
7 purchase totals =	$972.00		$1,073.3838	$1,073.38	$1,073.40	$1,073.40