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	$178.86	3.855%	$185.7551	$185.76	$185.75	$185.80
Purchase #2	$161.38	4.488%	$168.6227	$168.62	$168.60	$168.60
Purchase #3	$233.40	9.148%	$254.7514	$254.75	$254.75	$254.80
Purchase #4	$218.28	4.237%	$227.5285	$227.53	$227.55	$227.50
Purchase #5	$11.57	10.457%	$12.7799	$12.78	$12.80	$12.80
Purchase #6	$19.37	9.251%	$21.1619	$21.16	$21.15	$21.20
Purchase #7	$31.42	7.305%	$33.7152	$33.72	$33.70	$33.70
7 purchase totals =	$854.28		$904.3147	$904.32	$904.30	$904.40