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	$161.38	12.483%	$181.5251	$181.53	$181.55	$181.50
Purchase #2	$151.31	3.634%	$156.8086	$156.81	$156.80	$156.80
Purchase #3	$188.59	6.450%	$200.7541	$200.75	$200.75	$200.80
Purchase #4	$185.97	7.644%	$200.1855	$200.19	$200.20	$200.20
Purchase #5	$249.31	6.238%	$264.862	$264.86	$264.85	$264.90
Purchase #6	$23.49	10.348%	$25.9207	$25.92	$25.90	$25.90
Purchase #7	$208.51	12.157%	$233.8586	$233.86	$233.85	$233.90
7 purchase totals =	$1,168.56		$1,263.9146	$1,263.92	$1,263.90	$1,264.00