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	$243.38	11.461%	$271.2738	$271.27	$271.25	$271.30
Purchase #2	$200.27	13.542%	$227.3906	$227.39	$227.40	$227.40
Purchase #3	$63.97	13.217%	$72.4249	$72.42	$72.40	$72.40
Purchase #4	$236.75	5.567%	$249.9299	$249.93	$249.95	$249.90
Purchase #5	$210.88	5.530%	$222.5417	$222.54	$222.55	$222.50
Purchase #6	$79.55	7.785%	$85.743	$85.74	$85.75	$85.70
Purchase #7	$81.67	13.839%	$92.9723	$92.97	$92.95	$93.00
7 purchase totals =	$1,116.47		$1,222.2762	$1,222.26	$1,222.25	$1,222.20