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	$72.51	4.474%	$75.7541	$75.75	$75.75	$75.80
Purchase #2	$113.75	3.189%	$117.3775	$117.38	$117.40	$117.40
Purchase #3	$92.34	7.542%	$99.3043	$99.30	$99.30	$99.30
Purchase #4	$159.37	5.817%	$168.6406	$168.64	$168.65	$168.60
Purchase #5	$147.83	13.117%	$167.2209	$167.22	$167.20	$167.20
Purchase #6	$150.88	13.370%	$171.0527	$171.05	$171.05	$171.10
Purchase #7	$225.35	13.109%	$254.8911	$254.89	$254.90	$254.90
7 purchase totals =	$962.03		$1,054.2412	$1,054.23	$1,054.25	$1,054.30