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	$36.54	3.648%	$37.873	$37.87	$37.85	$37.90
Purchase #2	$209.87	9.384%	$229.5642	$229.56	$229.55	$229.60
Purchase #3	$30.61	11.501%	$34.1305	$34.13	$34.15	$34.10
Purchase #4	$213.88	13.331%	$242.3923	$242.39	$242.40	$242.40
Purchase #5	$107.29	8.238%	$116.1286	$116.13	$116.15	$116.10
Purchase #6	$109.84	8.254%	$118.9062	$118.91	$118.90	$118.90
Purchase #7	$219.26	11.851%	$245.2445	$245.24	$245.25	$245.20
7 purchase totals =	$927.29		$1,024.2393	$1,024.23	$1,024.25	$1,024.20