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	$163.50	3.117%	$168.5963	$168.60	$168.60	$168.60
Purchase #2	$85.41	3.220%	$88.1602	$88.16	$88.15	$88.20
Purchase #3	$215.52	13.470%	$244.5505	$244.55	$244.55	$244.60
Purchase #4	$71.47	9.501%	$78.2604	$78.26	$78.25	$78.30
Purchase #5	$239.68	7.268%	$257.0999	$257.10	$257.10	$257.10
Purchase #6	$89.85	11.200%	$99.9132	$99.91	$99.90	$99.90
Purchase #7	$83.89	7.335%	$90.0433	$90.04	$90.05	$90.00
7 purchase totals =	$949.32		$1,026.6238	$1,026.62	$1,026.60	$1,026.70