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	$151.64	3.158%	$156.4288	$156.43	$156.45	$156.40
Purchase #2	$71.44	12.464%	$80.3443	$80.34	$80.35	$80.30
Purchase #3	$65.39	10.802%	$72.4534	$72.45	$72.45	$72.50
Purchase #4	$206.65	6.493%	$220.0678	$220.07	$220.05	$220.10
Purchase #5	$33.88	10.612%	$37.4753	$37.48	$37.50	$37.50
Purchase #6	$55.98	5.738%	$59.1921	$59.19	$59.20	$59.20
Purchase #7	$150.56	5.764%	$159.2383	$159.24	$159.25	$159.20
7 purchase totals =	$735.54		$785.2000	$785.20	$785.25	$785.20