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	$78.37	4.289%	$81.7313	$81.73	$81.75	$81.70
Purchase #2	$54.47	12.538%	$61.2994	$61.30	$61.30	$61.30
Purchase #3	$199.57	6.309%	$212.1609	$212.16	$212.15	$212.20
Purchase #4	$138.49	8.872%	$150.7768	$150.78	$150.80	$150.80
Purchase #5	$51.97	11.449%	$57.92	$57.92	$57.90	$57.90
Purchase #6	$125.95	9.463%	$137.8686	$137.87	$137.85	$137.90
Purchase #7	$114.96	7.685%	$123.7947	$123.79	$123.80	$123.80
7 purchase totals =	$763.78		$825.5517	$825.55	$825.55	$825.60