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	$178.43	10.305%	$196.8172	$196.82	$196.80	$196.80
Purchase #2	$158.62	8.251%	$171.7077	$171.71	$171.70	$171.70
Purchase #3	$247.38	4.816%	$259.2938	$259.29	$259.30	$259.30
Purchase #4	$118.27	8.303%	$128.09	$128.09	$128.10	$128.10
Purchase #5	$30.90	3.656%	$32.0297	$32.03	$32.05	$32.00
Purchase #6	$212.94	7.817%	$229.5855	$229.59	$229.60	$229.60
Purchase #7	$221.73	7.201%	$237.6968	$237.70	$237.70	$237.70
7 purchase totals =	$1,168.27		$1,255.2207	$1,255.23	$1,255.25	$1,255.20