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	$180.87	8.821%	$196.8245	$196.82	$196.80	$196.80
Purchase #2	$69.33	3.246%	$71.5805	$71.58	$71.60	$71.60
Purchase #3	$230.60	11.651%	$257.4672	$257.47	$257.45	$257.50
Purchase #4	$6.77	5.233%	$7.1243	$7.12	$7.10	$7.10
Purchase #5	$139.76	5.200%	$147.0275	$147.03	$147.05	$147.00
Purchase #6	$243.94	6.246%	$259.1765	$259.18	$259.20	$259.20
Purchase #7	$207.32	12.744%	$233.7409	$233.74	$233.75	$233.70
7 purchase totals =	$1,078.59		$1,172.9414	$1,172.94	$1,172.95	$1,172.90