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	$72.89	3.526%	$75.4601	$75.46	$75.45	$75.50
Purchase #2	$68.28	5.330%	$71.9193	$71.92	$71.90	$71.90
Purchase #3	$40.65	5.687%	$42.9618	$42.96	$42.95	$43.00
Purchase #4	$184.61	12.710%	$208.0739	$208.07	$208.05	$208.10
Purchase #5	$216.94	7.782%	$233.8223	$233.82	$233.80	$233.80
Purchase #6	$213.69	6.362%	$227.285	$227.29	$227.30	$227.30
Purchase #7	$221.61	12.282%	$248.8281	$248.83	$248.85	$248.80
7 purchase totals =	$1,018.67		$1,108.3505	$1,108.35	$1,108.30	$1,108.40