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	$172.59	4.265%	$179.951	$179.95	$179.95	$180.00
Purchase #2	$80.89	12.344%	$90.8751	$90.88	$90.90	$90.90
Purchase #3	$176.75	3.871%	$183.592	$183.59	$183.60	$183.60
Purchase #4	$123.33	10.194%	$135.9023	$135.90	$135.90	$135.90
Purchase #5	$152.94	11.629%	$170.7254	$170.73	$170.75	$170.70
Purchase #6	$230.68	10.102%	$253.9833	$253.98	$254.00	$254.00
Purchase #7	$68.41	4.436%	$71.4447	$71.44	$71.45	$71.40
7 purchase totals =	$1,005.59		$1,086.4738	$1,086.47	$1,086.55	$1,086.50