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	$126.81	4.386%	$132.3719	$132.37	$132.35	$132.40
Purchase #2	$54.93	12.182%	$61.6216	$61.62	$61.60	$61.60
Purchase #3	$90.97	9.225%	$99.362	$99.36	$99.35	$99.40
Purchase #4	$62.58	4.110%	$65.152	$65.15	$65.15	$65.20
Purchase #5	$67.44	3.489%	$69.793	$69.79	$69.80	$69.80
Purchase #6	$204.36	8.783%	$222.3089	$222.31	$222.30	$222.30
Purchase #7	$103.73	9.532%	$113.6175	$113.62	$113.60	$113.60
7 purchase totals =	$710.82		$764.2269	$764.22	$764.15	$764.30