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	$110.64	3.578%	$114.5987	$114.60	$114.60	$114.60
Purchase #2	$55.91	6.112%	$59.3272	$59.33	$59.35	$59.30
Purchase #3	$206.52	11.447%	$230.1603	$230.16	$230.15	$230.20
Purchase #4	$147.86	4.570%	$154.6172	$154.62	$154.60	$154.60
Purchase #5	$228.53	7.317%	$245.2515	$245.25	$245.25	$245.30
Purchase #6	$77.62	5.825%	$82.1414	$82.14	$82.15	$82.10
Purchase #7	$57.78	7.317%	$62.0078	$62.01	$62.00	$62.00
7 purchase totals =	$884.86		$948.1041	$948.11	$948.10	$948.10