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	$55.92	11.432%	$62.3128	$62.31	$62.30	$62.30
Purchase #2	$68.28	10.560%	$75.4904	$75.49	$75.50	$75.50
Purchase #3	$28.29	13.550%	$32.1233	$32.12	$32.10	$32.10
Purchase #4	$78.58	10.154%	$86.559	$86.56	$86.55	$86.60
Purchase #5	$148.94	5.813%	$157.5979	$157.60	$157.60	$157.60
Purchase #6	$35.87	3.806%	$37.2352	$37.24	$37.25	$37.20
Purchase #7	$80.94	11.183%	$89.9915	$89.99	$90.00	$90.00
7 purchase totals =	$496.82		$541.3101	$541.31	$541.30	$541.30