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	$75.87	11.627%	$84.6914	$84.69	$84.70	$84.70
Purchase #2	$140.91	7.229%	$151.0964	$151.10	$151.10	$151.10
Purchase #3	$201.53	12.371%	$226.4613	$226.46	$226.45	$226.50
Purchase #4	$171.34	8.155%	$185.3128	$185.31	$185.30	$185.30
Purchase #5	$143.32	5.706%	$151.4978	$151.50	$151.50	$151.50
Purchase #6	$160.63	7.454%	$172.6034	$172.60	$172.60	$172.60
Purchase #7	$110.49	3.399%	$114.2456	$114.25	$114.25	$114.20
7 purchase totals =	$1,004.09		$1,085.9087	$1,085.91	$1,085.90	$1,085.90