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	$119.98	6.461%	$127.7319	$127.73	$127.75	$127.70
Purchase #2	$158.56	6.429%	$168.7538	$168.75	$168.75	$168.80
Purchase #3	$213.74	6.135%	$226.8529	$226.85	$226.85	$226.90
Purchase #4	$183.57	3.781%	$190.5108	$190.51	$190.50	$190.50
Purchase #5	$223.77	5.570%	$236.234	$236.23	$236.25	$236.20
Purchase #6	$179.61	3.667%	$186.1963	$186.20	$186.20	$186.20
Purchase #7	$33.29	9.820%	$36.5591	$36.56	$36.55	$36.60
7 purchase totals =	$1,112.52		$1,172.8388	$1,172.83	$1,172.85	$1,172.90