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	$244.75	4.613%	$256.0403	$256.04	$256.05	$256.00
Purchase #2	$17.32	12.495%	$19.4841	$19.48	$19.50	$19.50
Purchase #3	$96.40	11.375%	$107.3655	$107.37	$107.35	$107.40
Purchase #4	$127.44	11.634%	$142.2664	$142.27	$142.25	$142.30
Purchase #5	$98.88	10.108%	$108.8748	$108.87	$108.85	$108.90
Purchase #6	$79.57	7.796%	$85.7733	$85.77	$85.75	$85.80
Purchase #7	$49.89	7.359%	$53.5614	$53.56	$53.55	$53.60
7 purchase totals =	$714.25		$773.3658	$773.36	$773.30	$773.50