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	$143.44	3.589%	$148.5881	$148.59	$148.60	$148.60
Purchase #2	$95.72	3.771%	$99.3296	$99.33	$99.35	$99.30
Purchase #3	$110.92	3.544%	$114.851	$114.85	$114.85	$114.90
Purchase #4	$70.59	10.544%	$78.033	$78.03	$78.05	$78.00
Purchase #5	$166.34	9.448%	$182.0558	$182.06	$182.05	$182.10
Purchase #6	$68.80	7.761%	$74.1396	$74.14	$74.15	$74.10
Purchase #7	$49.27	8.810%	$53.6107	$53.61	$53.60	$53.60
7 purchase totals =	$705.08		$750.6078	$750.61	$750.65	$750.60