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	$116.35	12.696%	$131.1218	$131.12	$131.10	$131.10
Purchase #2	$181.95	10.104%	$200.3342	$200.33	$200.35	$200.30
Purchase #3	$91.34	4.444%	$95.3991	$95.40	$95.40	$95.40
Purchase #4	$166.50	4.797%	$174.487	$174.49	$174.50	$174.50
Purchase #5	$81.73	5.799%	$86.4695	$86.47	$86.45	$86.50
Purchase #6	$207.44	3.234%	$214.1486	$214.15	$214.15	$214.10
Purchase #7	$93.58	3.145%	$96.5231	$96.52	$96.50	$96.50
7 purchase totals =	$938.89		$998.4833	$998.48	$998.45	$998.40