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	$117.69	11.200%	$130.8713	$130.87	$130.85	$130.90
Purchase #2	$47.56	7.650%	$51.1983	$51.20	$51.20	$51.20
Purchase #3	$78.45	8.869%	$85.4077	$85.41	$85.40	$85.40
Purchase #4	$165.43	12.613%	$186.2957	$186.30	$186.30	$186.30
Purchase #5	$224.81	3.133%	$231.8533	$231.85	$231.85	$231.90
Purchase #6	$194.69	7.492%	$209.2762	$209.28	$209.30	$209.30
Purchase #7	$75.74	10.390%	$83.6094	$83.61	$83.60	$83.60
7 purchase totals =	$904.37		$978.5119	$978.52	$978.50	$978.60