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	$233.91	3.685%	$242.5296	$242.53	$242.55	$242.50
Purchase #2	$30.56	7.828%	$32.9522	$32.95	$32.95	$33.00
Purchase #3	$99.57	9.786%	$109.3139	$109.31	$109.30	$109.30
Purchase #4	$53.35	11.174%	$59.3113	$59.31	$59.30	$59.30
Purchase #5	$220.96	6.831%	$236.0538	$236.05	$236.05	$236.10
Purchase #6	$111.57	10.816%	$123.6374	$123.64	$123.65	$123.60
Purchase #7	$127.30	10.621%	$140.8205	$140.82	$140.80	$140.80
7 purchase totals =	$877.22		$944.6187	$944.61	$944.60	$944.60