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	$231.98	12.268%	$260.4393	$260.44	$260.45	$260.40
Purchase #2	$147.33	6.504%	$156.9123	$156.91	$156.90	$156.90
Purchase #3	$211.78	9.290%	$231.4544	$231.45	$231.45	$231.50
Purchase #4	$24.49	12.185%	$27.4741	$27.47	$27.45	$27.50
Purchase #5	$76.48	6.513%	$81.4611	$81.46	$81.45	$81.50
Purchase #6	$103.67	13.644%	$117.8147	$117.81	$117.80	$117.80
Purchase #7	$221.76	5.459%	$233.8659	$233.87	$233.85	$233.90
7 purchase totals =	$1,017.49		$1,109.4218	$1,109.41	$1,109.35	$1,109.50