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	$224.79	4.245%	$234.3323	$234.33	$234.35	$234.30
Purchase #2	$64.72	11.673%	$72.2748	$72.27	$72.25	$72.30
Purchase #3	$104.26	4.837%	$109.3031	$109.30	$109.30	$109.30
Purchase #4	$218.77	12.652%	$246.4488	$246.45	$246.45	$246.40
Purchase #5	$146.35	3.740%	$151.8235	$151.82	$151.80	$151.80
Purchase #6	$147.46	4.345%	$153.8671	$153.87	$153.85	$153.90
Purchase #7	$38.70	9.122%	$42.2302	$42.23	$42.25	$42.20
7 purchase totals =	$945.05		$1,010.2798	$1,010.27	$1,010.25	$1,010.20