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	$206.54	8.618%	$224.3396	$224.34	$224.35	$224.30
Purchase #2	$65.82	8.370%	$71.3291	$71.33	$71.35	$71.30
Purchase #3	$153.79	4.594%	$160.8551	$160.86	$160.85	$160.90
Purchase #4	$130.37	13.803%	$148.365	$148.37	$148.35	$148.40
Purchase #5	$202.97	7.486%	$218.1643	$218.16	$218.15	$218.20
Purchase #6	$77.69	9.748%	$85.2632	$85.26	$85.25	$85.30
Purchase #7	$83.77	12.357%	$94.1215	$94.12	$94.10	$94.10
7 purchase totals =	$920.95		$1,002.4378	$1,002.44	$1,002.40	$1,002.50