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	$79.54	5.220%	$83.692	$83.69	$83.70	$83.70
Purchase #2	$87.97	13.772%	$100.0852	$100.09	$100.10	$100.10
Purchase #3	$101.88	8.113%	$110.1455	$110.15	$110.15	$110.10
Purchase #4	$181.85	9.524%	$199.1694	$199.17	$199.15	$199.20
Purchase #5	$45.90	13.520%	$52.1057	$52.11	$52.10	$52.10
Purchase #6	$113.31	6.379%	$120.538	$120.54	$120.55	$120.50
Purchase #7	$169.66	6.461%	$180.6217	$180.62	$180.60	$180.60
7 purchase totals =	$780.11		$846.3575	$846.37	$846.35	$846.30