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	$162.28	4.335%	$169.3148	$169.31	$169.30	$169.30
Purchase #2	$62.43	10.696%	$69.1075	$69.11	$69.10	$69.10
Purchase #3	$110.32	9.573%	$120.8809	$120.88	$120.90	$120.90
Purchase #4	$123.98	10.810%	$137.3822	$137.38	$137.40	$137.40
Purchase #5	$99.53	3.782%	$103.2942	$103.29	$103.30	$103.30
Purchase #6	$124.52	13.511%	$141.3439	$141.34	$141.35	$141.30
Purchase #7	$31.37	5.869%	$33.2111	$33.21	$33.20	$33.20
7 purchase totals =	$714.43		$774.5346	$774.52	$774.55	$774.50