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	$228.29	13.220%	$258.4699	$258.47	$258.45	$258.50
Purchase #2	$191.79	10.525%	$211.9759	$211.98	$212.00	$212.00
Purchase #3	$25.46	6.137%	$27.0225	$27.02	$27.00	$27.00
Purchase #4	$98.92	12.646%	$111.4294	$111.43	$111.45	$111.40
Purchase #5	$239.41	6.759%	$255.5917	$255.59	$255.60	$255.60
Purchase #6	$8.96	13.827%	$10.1989	$10.20	$10.20	$10.20
Purchase #7	$245.78	10.571%	$271.7614	$271.76	$271.75	$271.80
7 purchase totals =	$1,038.61		$1,146.4497	$1,146.45	$1,146.45	$1,146.50