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	$184.73	6.102%	$196.0022	$196.00	$196.00	$196.00
Purchase #2	$136.97	8.440%	$148.5303	$148.53	$148.55	$148.50
Purchase #3	$152.56	5.166%	$160.4412	$160.44	$160.45	$160.40
Purchase #4	$183.83	5.867%	$194.6153	$194.62	$194.60	$194.60
Purchase #5	$37.50	8.129%	$40.5484	$40.55	$40.55	$40.50
Purchase #6	$41.96	7.568%	$45.1355	$45.14	$45.15	$45.10
Purchase #7	$173.98	6.696%	$185.6297	$185.63	$185.65	$185.60
7 purchase totals =	$911.53		$970.9026	$970.91	$970.95	$970.70