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	$152.93	6.524%	$162.9072	$162.91	$162.90	$162.90
Purchase #2	$181.35	7.318%	$194.6212	$194.62	$194.60	$194.60
Purchase #3	$90.90	10.381%	$100.3363	$100.34	$100.35	$100.30
Purchase #4	$48.82	13.332%	$55.3287	$55.33	$55.35	$55.30
Purchase #5	$124.58	12.193%	$139.77	$139.77	$139.75	$139.80
Purchase #6	$191.86	13.370%	$217.5117	$217.51	$217.50	$217.50
Purchase #7	$72.67	7.618%	$78.206	$78.21	$78.20	$78.20
7 purchase totals =	$863.11		$948.6811	$948.69	$948.65	$948.60