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	$213.83	8.162%	$231.2828	$231.28	$231.30	$231.30
Purchase #2	$15.31	3.178%	$15.7966	$15.80	$15.80	$15.80
Purchase #3	$39.31	10.411%	$43.4026	$43.40	$43.40	$43.40
Purchase #4	$137.48	12.755%	$155.0156	$155.02	$155.00	$155.00
Purchase #5	$218.83	13.272%	$247.8731	$247.87	$247.85	$247.90
Purchase #6	$152.62	12.300%	$171.3923	$171.39	$171.40	$171.40
Purchase #7	$80.99	10.869%	$89.7928	$89.79	$89.80	$89.80
7 purchase totals =	$858.37		$954.5558	$954.55	$954.55	$954.60