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	$142.96	5.861%	$151.3389	$151.34	$151.35	$151.30
Purchase #2	$72.80	4.809%	$76.301	$76.30	$76.30	$76.30
Purchase #3	$104.98	4.429%	$109.6296	$109.63	$109.65	$109.60
Purchase #4	$133.48	10.587%	$147.6115	$147.61	$147.60	$147.60
Purchase #5	$46.27	10.170%	$50.9757	$50.98	$51.00	$51.00
Purchase #6	$150.32	10.598%	$166.2509	$166.25	$166.25	$166.30
Purchase #7	$248.42	6.356%	$264.2096	$264.21	$264.20	$264.20
7 purchase totals =	$899.23		$966.3172	$966.32	$966.35	$966.30