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	$134.42	13.592%	$152.6904	$152.69	$152.70	$152.70
Purchase #2	$240.78	7.193%	$258.0993	$258.10	$258.10	$258.10
Purchase #3	$91.54	4.240%	$95.4213	$95.42	$95.40	$95.40
Purchase #4	$143.63	4.288%	$149.7889	$149.79	$149.80	$149.80
Purchase #5	$104.35	8.705%	$113.4337	$113.43	$113.45	$113.40
Purchase #6	$86.72	4.727%	$90.8193	$90.82	$90.80	$90.80
Purchase #7	$219.92	10.589%	$243.2073	$243.21	$243.20	$243.20
7 purchase totals =	$1,021.36		$1,103.4602	$1,103.46	$1,103.45	$1,103.40