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	$160.89	8.237%	$174.1425	$174.14	$174.15	$174.10
Purchase #2	$151.53	8.712%	$164.7313	$164.73	$164.75	$164.70
Purchase #3	$171.93	7.849%	$185.4248	$185.42	$185.40	$185.40
Purchase #4	$81.61	11.825%	$91.2604	$91.26	$91.25	$91.30
Purchase #5	$111.69	13.852%	$127.1613	$127.16	$127.15	$127.20
Purchase #6	$39.45	12.407%	$44.3446	$44.34	$44.35	$44.30
Purchase #7	$203.90	11.461%	$227.269	$227.27	$227.25	$227.30
7 purchase totals =	$921.00		$1,014.3339	$1,014.32	$1,014.30	$1,014.30