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	$168.95	11.657%	$188.6445	$188.64	$188.65	$188.60
Purchase #2	$54.96	9.430%	$60.1427	$60.14	$60.15	$60.10
Purchase #3	$94.56	5.121%	$99.4024	$99.40	$99.40	$99.40
Purchase #4	$90.84	4.447%	$94.8797	$94.88	$94.90	$94.90
Purchase #5	$231.81	5.112%	$243.6601	$243.66	$243.65	$243.70
Purchase #6	$92.56	7.364%	$99.3761	$99.38	$99.40	$99.40
Purchase #7	$131.80	12.246%	$147.9402	$147.94	$147.95	$147.90
7 purchase totals =	$865.48		$934.0457	$934.04	$934.10	$934.00