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	$113.96	5.440%	$120.1594	$120.16	$120.15	$120.20
Purchase #2	$187.77	12.515%	$211.2694	$211.27	$211.25	$211.30
Purchase #3	$244.56	7.761%	$263.5403	$263.54	$263.55	$263.50
Purchase #4	$38.84	10.468%	$42.9058	$42.91	$42.90	$42.90
Purchase #5	$132.71	10.472%	$146.6074	$146.61	$146.60	$146.60
Purchase #6	$222.59	5.309%	$234.4073	$234.41	$234.40	$234.40
Purchase #7	$141.30	3.295%	$145.9558	$145.96	$145.95	$146.00
7 purchase totals =	$1,081.73		$1,164.8454	$1,164.86	$1,164.80	$1,164.90