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	$58.95	10.155%	$64.9364	$64.94	$64.95	$64.90
Purchase #2	$168.82	3.214%	$174.2459	$174.25	$174.25	$174.20
Purchase #3	$53.73	11.450%	$59.8821	$59.88	$59.90	$59.90
Purchase #4	$93.57	5.862%	$99.0551	$99.06	$99.05	$99.10
Purchase #5	$113.26	13.810%	$128.9012	$128.90	$128.90	$128.90
Purchase #6	$214.62	8.738%	$233.3735	$233.37	$233.35	$233.40
Purchase #7	$221.63	3.343%	$229.0391	$229.04	$229.05	$229.00
7 purchase totals =	$924.58		$989.4333	$989.44	$989.45	$989.40