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	$87.27	7.772%	$94.0526	$94.05	$94.05	$94.10
Purchase #2	$164.92	10.586%	$182.3784	$182.38	$182.40	$182.40
Purchase #3	$97.70	3.635%	$101.2514	$101.25	$101.25	$101.30
Purchase #4	$137.81	6.385%	$146.6092	$146.61	$146.60	$146.60
Purchase #5	$75.57	5.103%	$79.4263	$79.43	$79.45	$79.40
Purchase #6	$222.90	9.226%	$243.4648	$243.46	$243.45	$243.50
Purchase #7	$236.96	11.671%	$264.6156	$264.62	$264.60	$264.60
7 purchase totals =	$1,023.13		$1,111.7983	$1,111.80	$1,111.80	$1,111.90