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	$137.90	5.737%	$145.8113	$145.81	$145.80	$145.80
Purchase #2	$5.55	13.127%	$6.2785	$6.28	$6.30	$6.30
Purchase #3	$74.96	4.637%	$78.4359	$78.44	$78.45	$78.40
Purchase #4	$200.62	6.224%	$213.1066	$213.11	$213.10	$213.10
Purchase #5	$97.65	12.512%	$109.868	$109.87	$109.85	$109.90
Purchase #6	$96.93	3.428%	$100.2528	$100.25	$100.25	$100.30
Purchase #7	$135.89	11.212%	$151.126	$151.13	$151.15	$151.10
7 purchase totals =	$749.50		$804.8791	$804.89	$804.90	$804.90