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	$75.89	8.696%	$82.4894	$82.49	$82.50	$82.50
Purchase #2	$245.92	13.154%	$278.2683	$278.27	$278.25	$278.30
Purchase #3	$95.85	3.262%	$98.9766	$98.98	$99.00	$99.00
Purchase #4	$243.69	6.587%	$259.7419	$259.74	$259.75	$259.70
Purchase #5	$64.30	11.864%	$71.9286	$71.93	$71.95	$71.90
Purchase #6	$35.68	4.567%	$37.3095	$37.31	$37.30	$37.30
Purchase #7	$194.65	11.347%	$216.7369	$216.74	$216.75	$216.70
7 purchase totals =	$955.98		$1,045.4512	$1,045.46	$1,045.50	$1,045.40