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	$160.90	4.563%	$168.2419	$168.24	$168.25	$168.20
Purchase #2	$10.33	3.327%	$10.6737	$10.67	$10.65	$10.70
Purchase #3	$220.61	10.158%	$243.0196	$243.02	$243.00	$243.00
Purchase #4	$150.53	6.362%	$160.1067	$160.11	$160.10	$160.10
Purchase #5	$209.75	13.631%	$238.341	$238.34	$238.35	$238.30
Purchase #6	$148.76	13.482%	$168.8158	$168.82	$168.80	$168.80
Purchase #7	$76.91	12.172%	$86.2715	$86.27	$86.25	$86.30
7 purchase totals =	$977.79		$1,075.4702	$1,075.47	$1,075.40	$1,075.40