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	$148.25	11.104%	$164.7117	$164.71	$164.70	$164.70
Purchase #2	$185.89	10.187%	$204.8266	$204.83	$204.85	$204.80
Purchase #3	$196.33	3.364%	$202.9345	$202.93	$202.95	$202.90
Purchase #4	$90.42	11.356%	$100.6881	$100.69	$100.70	$100.70
Purchase #5	$93.78	9.111%	$102.3243	$102.32	$102.30	$102.30
Purchase #6	$134.44	13.751%	$152.9268	$152.93	$152.95	$152.90
Purchase #7	$71.85	3.502%	$74.3662	$74.37	$74.35	$74.40
7 purchase totals =	$920.96		$1,002.7782	$1,002.78	$1,002.80	$1,002.70