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	$184.98	6.155%	$196.3655	$196.37	$196.35	$196.40
Purchase #2	$35.27	5.181%	$37.0973	$37.10	$37.10	$37.10
Purchase #3	$141.73	3.477%	$146.658	$146.66	$146.65	$146.70
Purchase #4	$94.73	11.144%	$105.2867	$105.29	$105.30	$105.30
Purchase #5	$80.37	9.391%	$87.9175	$87.92	$87.90	$87.90
Purchase #6	$130.63	6.712%	$139.3979	$139.40	$139.40	$139.40
Purchase #7	$206.37	4.734%	$216.1396	$216.14	$216.15	$216.10
7 purchase totals =	$874.08		$928.8625	$928.88	$928.85	$928.90