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	$235.29	11.695%	$262.8072	$262.81	$262.80	$262.80
Purchase #2	$41.78	3.183%	$43.1099	$43.11	$43.10	$43.10
Purchase #3	$88.89	11.580%	$99.1835	$99.18	$99.20	$99.20
Purchase #4	$168.44	7.292%	$180.7226	$180.72	$180.70	$180.70
Purchase #5	$38.39	11.713%	$42.8866	$42.89	$42.90	$42.90
Purchase #6	$161.47	5.736%	$170.7319	$170.73	$170.75	$170.70
Purchase #7	$32.83	7.175%	$35.1856	$35.19	$35.20	$35.20
7 purchase totals =	$767.09		$834.6273	$834.63	$834.65	$834.60