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	$180.93	4.713%	$189.4572	$189.46	$189.45	$189.50
Purchase #2	$194.45	13.622%	$220.938	$220.94	$220.95	$220.90
Purchase #3	$90.26	7.329%	$96.8752	$96.88	$96.90	$96.90
Purchase #4	$127.37	13.792%	$144.9369	$144.94	$144.95	$144.90
Purchase #5	$89.27	11.288%	$99.3468	$99.35	$99.35	$99.30
Purchase #6	$185.72	13.766%	$211.2862	$211.29	$211.30	$211.30
Purchase #7	$202.51	11.445%	$225.6873	$225.69	$225.70	$225.70
7 purchase totals =	$1,070.51		$1,188.5276	$1,188.55	$1,188.60	$1,188.50