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	$173.36	10.430%	$191.4414	$191.44	$191.45	$191.40
Purchase #2	$91.80	7.536%	$98.718	$98.72	$98.70	$98.70
Purchase #3	$223.48	5.795%	$236.4307	$236.43	$236.45	$236.40
Purchase #4	$23.78	7.420%	$25.5445	$25.54	$25.55	$25.50
Purchase #5	$100.61	10.671%	$111.3461	$111.35	$111.35	$111.30
Purchase #6	$193.33	10.451%	$213.5349	$213.53	$213.55	$213.50
Purchase #7	$111.82	11.424%	$124.5943	$124.59	$124.60	$124.60
7 purchase totals =	$918.18		$1,001.6099	$1,001.60	$1,001.65	$1,001.40