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	$87.82	9.650%	$96.2946	$96.29	$96.30	$96.30
Purchase #2	$134.72	7.143%	$144.343	$144.34	$144.35	$144.30
Purchase #3	$19.32	4.597%	$20.2081	$20.21	$20.20	$20.20
Purchase #4	$107.31	9.598%	$117.6096	$117.61	$117.60	$117.60
Purchase #5	$61.81	9.425%	$67.6356	$67.64	$67.65	$67.60
Purchase #6	$106.44	11.574%	$118.7594	$118.76	$118.75	$118.80
Purchase #7	$56.86	9.312%	$62.1548	$62.15	$62.15	$62.20
7 purchase totals =	$574.28		$627.0051	$627.00	$627.00	$627.00