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	$151.83	4.567%	$158.7641	$158.76	$158.75	$158.80
Purchase #2	$198.47	7.535%	$213.4247	$213.42	$213.40	$213.40
Purchase #3	$243.58	4.605%	$254.7969	$254.80	$254.80	$254.80
Purchase #4	$248.91	5.446%	$262.4656	$262.47	$262.45	$262.50
Purchase #5	$197.56	5.700%	$208.8209	$208.82	$208.80	$208.80
Purchase #6	$50.29	3.650%	$52.1256	$52.13	$52.15	$52.10
Purchase #7	$52.38	3.661%	$54.2976	$54.30	$54.30	$54.30
7 purchase totals =	$1,143.02		$1,204.6954	$1,204.70	$1,204.65	$1,204.70