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	$134.73	11.728%	$150.5311	$150.53	$150.55	$150.50
Purchase #2	$32.39	9.305%	$35.4039	$35.40	$35.40	$35.40
Purchase #3	$123.77	3.266%	$127.8123	$127.81	$127.80	$127.80
Purchase #4	$181.59	7.391%	$195.0113	$195.01	$195.00	$195.00
Purchase #5	$209.52	3.703%	$217.2785	$217.28	$217.30	$217.30
Purchase #6	$243.61	8.481%	$264.2706	$264.27	$264.25	$264.30
Purchase #7	$29.90	13.790%	$34.0232	$34.02	$34.00	$34.00
7 purchase totals =	$955.51		$1,024.3309	$1,024.32	$1,024.30	$1,024.30