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	$109.33	7.310%	$117.322	$117.32	$117.30	$117.30
Purchase #2	$165.70	11.328%	$184.4705	$184.47	$184.45	$184.50
Purchase #3	$56.38	7.431%	$60.5696	$60.57	$60.55	$60.60
Purchase #4	$243.91	5.862%	$258.208	$258.21	$258.20	$258.20
Purchase #5	$113.76	12.686%	$128.1916	$128.19	$128.20	$128.20
Purchase #6	$244.85	13.827%	$278.7054	$278.71	$278.70	$278.70
Purchase #7	$182.27	7.794%	$196.4761	$196.48	$196.50	$196.50
7 purchase totals =	$1,116.20		$1,223.9432	$1,223.95	$1,223.90	$1,224.00