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	$76.47	12.167%	$85.7741	$85.77	$85.75	$85.80
Purchase #2	$162.62	10.216%	$179.2333	$179.23	$179.25	$179.20
Purchase #3	$220.53	6.685%	$235.2724	$235.27	$235.25	$235.30
Purchase #4	$156.44	12.158%	$175.46	$175.46	$175.45	$175.50
Purchase #5	$165.49	12.196%	$185.6732	$185.67	$185.65	$185.70
Purchase #6	$38.76	8.847%	$42.1891	$42.19	$42.20	$42.20
Purchase #7	$57.46	11.481%	$64.057	$64.06	$64.05	$64.10
7 purchase totals =	$877.77		$967.6591	$967.65	$967.60	$967.80