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	$66.93	8.415%	$72.5622	$72.56	$72.55	$72.60
Purchase #2	$156.64	10.367%	$172.8789	$172.88	$172.90	$172.90
Purchase #3	$243.86	12.815%	$275.1107	$275.11	$275.10	$275.10
Purchase #4	$185.72	3.458%	$192.1422	$192.14	$192.15	$192.10
Purchase #5	$42.28	7.747%	$45.5554	$45.56	$45.55	$45.60
Purchase #6	$206.86	6.789%	$220.9037	$220.90	$220.90	$220.90
Purchase #7	$206.97	11.464%	$230.697	$230.70	$230.70	$230.70
7 purchase totals =	$1,109.26		$1,209.8501	$1,209.85	$1,209.85	$1,209.90