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	$77.33	10.387%	$85.3623	$85.36	$85.35	$85.40
Purchase #2	$175.26	12.377%	$196.9519	$196.95	$196.95	$197.00
Purchase #3	$53.28	5.587%	$56.2568	$56.26	$56.25	$56.30
Purchase #4	$82.86	10.253%	$91.3556	$91.36	$91.35	$91.40
Purchase #5	$216.96	11.835%	$242.6372	$242.64	$242.65	$242.60
Purchase #6	$25.79	13.344%	$29.2314	$29.23	$29.25	$29.20
Purchase #7	$55.87	5.814%	$59.1183	$59.12	$59.10	$59.10
7 purchase totals =	$687.35		$760.9135	$760.92	$760.90	$761.00