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	$136.87	7.830%	$147.5869	$147.59	$147.60	$147.60
Purchase #2	$93.67	7.150%	$100.3674	$100.37	$100.35	$100.40
Purchase #3	$81.39	6.430%	$86.6234	$86.62	$86.60	$86.60
Purchase #4	$19.33	4.253%	$20.1521	$20.15	$20.15	$20.20
Purchase #5	$63.68	13.554%	$72.3112	$72.31	$72.30	$72.30
Purchase #6	$219.28	12.595%	$246.8983	$246.90	$246.90	$246.90
Purchase #7	$209.98	5.434%	$221.3903	$221.39	$221.40	$221.40
7 purchase totals =	$824.20		$895.3296	$895.33	$895.30	$895.40