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	$137.48	10.667%	$152.145	$152.15	$152.15	$152.10
Purchase #2	$173.92	4.164%	$181.162	$181.16	$181.15	$181.20
Purchase #3	$199.53	4.808%	$209.1234	$209.12	$209.10	$209.10
Purchase #4	$31.72	6.398%	$33.7494	$33.75	$33.75	$33.70
Purchase #5	$76.97	10.508%	$85.058	$85.06	$85.05	$85.10
Purchase #6	$13.55	11.785%	$15.1469	$15.15	$15.15	$15.10
Purchase #7	$187.77	5.409%	$197.9265	$197.93	$197.95	$197.90
7 purchase totals =	$820.94		$874.3112	$874.32	$874.30	$874.20