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	$247.81	6.222%	$263.2287	$263.23	$263.25	$263.20
Purchase #2	$43.80	9.489%	$47.9562	$47.96	$47.95	$48.00
Purchase #3	$58.63	11.866%	$65.587	$65.59	$65.60	$65.60
Purchase #4	$126.96	12.190%	$142.4364	$142.44	$142.45	$142.40
Purchase #5	$99.32	6.599%	$105.8741	$105.87	$105.85	$105.90
Purchase #6	$62.88	5.851%	$66.5591	$66.56	$66.55	$66.60
Purchase #7	$146.57	10.760%	$162.3409	$162.34	$162.35	$162.30
7 purchase totals =	$785.97		$853.9824	$853.99	$854.00	$854.00