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	$79.54	11.593%	$88.7611	$88.76	$88.75	$88.80
Purchase #2	$16.93	11.667%	$18.9052	$18.91	$18.90	$18.90
Purchase #3	$77.51	6.668%	$82.6784	$82.68	$82.70	$82.70
Purchase #4	$56.26	6.455%	$59.8916	$59.89	$59.90	$59.90
Purchase #5	$165.94	8.273%	$179.6682	$179.67	$179.65	$179.70
Purchase #6	$45.71	12.470%	$51.41	$51.41	$51.40	$51.40
Purchase #7	$195.43	8.606%	$212.2487	$212.25	$212.25	$212.20
7 purchase totals =	$637.32		$693.5632	$693.57	$693.55	$693.60