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	$175.93	10.582%	$194.5469	$194.55	$194.55	$194.50
Purchase #2	$191.58	10.214%	$211.148	$211.15	$211.15	$211.10
Purchase #3	$31.54	5.183%	$33.1747	$33.17	$33.15	$33.20
Purchase #4	$36.40	3.544%	$37.69	$37.69	$37.70	$37.70
Purchase #5	$145.82	13.493%	$165.4955	$165.50	$165.50	$165.50
Purchase #6	$204.42	8.441%	$221.6751	$221.68	$221.70	$221.70
Purchase #7	$101.31	10.401%	$111.8473	$111.85	$111.85	$111.80
7 purchase totals =	$887.00		$975.5775	$975.59	$975.60	$975.50