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	$206.68	7.526%	$222.2347	$222.23	$222.25	$222.20
Purchase #2	$172.64	8.619%	$187.5198	$187.52	$187.50	$187.50
Purchase #3	$145.94	9.608%	$159.9619	$159.96	$159.95	$160.00
Purchase #4	$55.38	11.708%	$61.8639	$61.86	$61.85	$61.90
Purchase #5	$175.60	5.506%	$185.2685	$185.27	$185.25	$185.30
Purchase #6	$246.31	11.694%	$275.1135	$275.11	$275.10	$275.10
Purchase #7	$92.58	8.752%	$100.6826	$100.68	$100.70	$100.70
7 purchase totals =	$1,095.13		$1,192.6449	$1,192.63	$1,192.60	$1,192.70