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	$209.90	4.809%	$219.9941	$219.99	$220.00	$220.00
Purchase #2	$86.41	13.807%	$98.3406	$98.34	$98.35	$98.30
Purchase #3	$170.53	7.104%	$182.6445	$182.64	$182.65	$182.60
Purchase #4	$36.66	11.219%	$40.7729	$40.77	$40.75	$40.80
Purchase #5	$37.31	6.631%	$39.784	$39.78	$39.80	$39.80
Purchase #6	$25.89	5.315%	$27.2661	$27.27	$27.25	$27.30
Purchase #7	$112.41	13.310%	$127.3718	$127.37	$127.35	$127.40
7 purchase totals =	$679.11		$736.1740	$736.16	$736.15	$736.20