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	$95.37	4.118%	$99.2973	$99.30	$99.30	$99.30
Purchase #2	$94.51	8.733%	$102.7636	$102.76	$102.75	$102.80
Purchase #3	$67.61	7.353%	$72.5814	$72.58	$72.60	$72.60
Purchase #4	$160.61	7.508%	$172.6686	$172.67	$172.65	$172.70
Purchase #5	$240.28	4.463%	$251.0037	$251.00	$251.00	$251.00
Purchase #6	$167.46	4.837%	$175.56	$175.56	$175.55	$175.60
Purchase #7	$101.87	12.737%	$114.8452	$114.85	$114.85	$114.80
7 purchase totals =	$927.71		$988.7198	$988.72	$988.70	$988.80