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	$35.27	5.686%	$37.2755	$37.28	$37.30	$37.30
Purchase #2	$164.87	4.846%	$172.8596	$172.86	$172.85	$172.90
Purchase #3	$195.43	3.682%	$202.6257	$202.63	$202.65	$202.60
Purchase #4	$94.79	4.130%	$98.7048	$98.70	$98.70	$98.70
Purchase #5	$244.48	8.241%	$264.6276	$264.63	$264.65	$264.60
Purchase #6	$64.60	4.693%	$67.6317	$67.63	$67.65	$67.60
Purchase #7	$38.72	3.873%	$40.2196	$40.22	$40.20	$40.20
7 purchase totals =	$838.16		$883.9445	$883.95	$884.00	$883.90