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	$181.76	5.282%	$191.3606	$191.36	$191.35	$191.40
Purchase #2	$156.50	3.793%	$162.436	$162.44	$162.45	$162.40
Purchase #3	$226.57	6.753%	$241.8703	$241.87	$241.85	$241.90
Purchase #4	$51.69	10.164%	$56.9438	$56.94	$56.95	$56.90
Purchase #5	$231.85	5.429%	$244.4371	$244.44	$244.45	$244.40
Purchase #6	$204.41	11.227%	$227.3591	$227.36	$227.35	$227.40
Purchase #7	$133.38	13.468%	$151.3436	$151.34	$151.35	$151.30
7 purchase totals =	$1,186.16		$1,275.7505	$1,275.75	$1,275.75	$1,275.70