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	$145.30	5.123%	$152.7437	$152.74	$152.75	$152.70
Purchase #2	$165.51	13.500%	$187.8539	$187.85	$187.85	$187.90
Purchase #3	$81.41	13.562%	$92.4508	$92.45	$92.45	$92.50
Purchase #4	$81.38	10.550%	$89.9656	$89.97	$89.95	$90.00
Purchase #5	$81.47	8.790%	$88.6312	$88.63	$88.65	$88.60
Purchase #6	$152.74	3.611%	$158.2554	$158.26	$158.25	$158.30
Purchase #7	$176.34	11.648%	$196.8801	$196.88	$196.90	$196.90
7 purchase totals =	$884.15		$966.7807	$966.78	$966.80	$966.90