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	$250.74	6.586%	$267.2537	$267.25	$267.25	$267.30
Purchase #2	$64.77	13.391%	$73.4434	$73.44	$73.45	$73.40
Purchase #3	$82.28	9.221%	$89.867	$89.87	$89.85	$89.90
Purchase #4	$47.79	13.759%	$54.3654	$54.37	$54.35	$54.40
Purchase #5	$51.32	11.871%	$57.4122	$57.41	$57.40	$57.40
Purchase #6	$15.95	11.223%	$17.7401	$17.74	$17.75	$17.70
Purchase #7	$151.43	9.789%	$166.2535	$166.25	$166.25	$166.30
7 purchase totals =	$664.28		$726.3353	$726.33	$726.30	$726.40