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	$171.84	10.426%	$189.756	$189.76	$189.75	$189.80
Purchase #2	$24.45	10.571%	$27.0346	$27.03	$27.05	$27.00
Purchase #3	$224.76	7.510%	$241.6395	$241.64	$241.65	$241.60
Purchase #4	$233.83	13.399%	$265.1609	$265.16	$265.15	$265.20
Purchase #5	$70.96	3.385%	$73.362	$73.36	$73.35	$73.40
Purchase #6	$150.70	4.771%	$157.8899	$157.89	$157.90	$157.90
Purchase #7	$59.61	3.335%	$61.598	$61.60	$61.60	$61.60
7 purchase totals =	$936.15		$1,016.4409	$1,016.44	$1,016.45	$1,016.50