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	$211.53	10.753%	$234.2758	$234.28	$234.30	$234.30
Purchase #2	$216.96	3.782%	$225.1654	$225.17	$225.15	$225.20
Purchase #3	$82.26	8.360%	$89.1369	$89.14	$89.15	$89.10
Purchase #4	$105.61	11.485%	$117.7393	$117.74	$117.75	$117.70
Purchase #5	$74.36	6.312%	$79.0536	$79.05	$79.05	$79.10
Purchase #6	$111.30	7.727%	$119.9002	$119.90	$119.90	$119.90
Purchase #7	$94.78	6.119%	$100.5796	$100.58	$100.60	$100.60
7 purchase totals =	$896.80		$965.8508	$965.86	$965.90	$965.90