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	$71.26	8.579%	$77.3734	$77.37	$77.35	$77.40
Purchase #2	$45.96	11.689%	$51.3323	$51.33	$51.35	$51.30
Purchase #3	$98.84	6.802%	$105.5631	$105.56	$105.55	$105.60
Purchase #4	$16.69	10.322%	$18.4127	$18.41	$18.40	$18.40
Purchase #5	$181.32	12.766%	$204.4673	$204.47	$204.45	$204.50
Purchase #6	$81.60	10.487%	$90.1574	$90.16	$90.15	$90.20
Purchase #7	$166.29	5.119%	$174.8024	$174.80	$174.80	$174.80
7 purchase totals =	$661.96		$722.1086	$722.10	$722.05	$722.20