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	$134.28	13.206%	$152.013	$152.01	$152.00	$152.00
Purchase #2	$93.85	8.483%	$101.8113	$101.81	$101.80	$101.80
Purchase #3	$225.80	10.346%	$249.1613	$249.16	$249.15	$249.20
Purchase #4	$155.46	5.579%	$164.1331	$164.13	$164.15	$164.10
Purchase #5	$50.55	4.579%	$52.8647	$52.86	$52.85	$52.90
Purchase #6	$159.98	13.167%	$181.0446	$181.04	$181.05	$181.00
Purchase #7	$169.80	8.578%	$184.3654	$184.37	$184.35	$184.40
7 purchase totals =	$989.72		$1,085.3934	$1,085.38	$1,085.35	$1,085.40