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	$146.41	5.595%	$154.6016	$154.60	$154.60	$154.60
Purchase #2	$227.59	4.401%	$237.6062	$237.61	$237.60	$237.60
Purchase #3	$14.44	9.342%	$15.789	$15.79	$15.80	$15.80
Purchase #4	$71.92	12.477%	$80.8935	$80.89	$80.90	$80.90
Purchase #5	$229.50	4.700%	$240.2865	$240.29	$240.30	$240.30
Purchase #6	$38.46	11.677%	$42.951	$42.95	$42.95	$43.00
Purchase #7	$152.56	12.740%	$171.9961	$172.00	$172.00	$172.00
7 purchase totals =	$880.88		$944.1239	$944.13	$944.15	$944.20