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	$98.59	11.164%	$109.5966	$109.60	$109.60	$109.60
Purchase #2	$50.31	13.723%	$57.214	$57.21	$57.20	$57.20
Purchase #3	$45.95	11.789%	$51.367	$51.37	$51.35	$51.40
Purchase #4	$38.58	9.143%	$42.1074	$42.11	$42.10	$42.10
Purchase #5	$55.93	8.831%	$60.8692	$60.87	$60.85	$60.90
Purchase #6	$185.61	6.456%	$197.593	$197.59	$197.60	$197.60
Purchase #7	$96.35	6.412%	$102.528	$102.53	$102.55	$102.50
7 purchase totals =	$571.32		$621.2752	$621.28	$621.25	$621.30