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	$82.53	10.867%	$91.4985	$91.50	$91.50	$91.50
Purchase #2	$149.30	11.293%	$166.1604	$166.16	$166.15	$166.20
Purchase #3	$77.31	11.621%	$86.2942	$86.29	$86.30	$86.30
Purchase #4	$133.40	4.607%	$139.5457	$139.55	$139.55	$139.50
Purchase #5	$11.60	7.454%	$12.4647	$12.46	$12.45	$12.50
Purchase #6	$82.53	4.805%	$86.4956	$86.50	$86.50	$86.50
Purchase #7	$186.42	9.129%	$203.4383	$203.44	$203.45	$203.40
7 purchase totals =	$723.09		$785.8974	$785.90	$785.90	$785.90