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	$124.94	5.829%	$132.2228	$132.22	$132.20	$132.20
Purchase #2	$25.31	10.182%	$27.8871	$27.89	$27.90	$27.90
Purchase #3	$12.66	13.117%	$14.3206	$14.32	$14.30	$14.30
Purchase #4	$182.47	7.654%	$196.4363	$196.44	$196.45	$196.40
Purchase #5	$71.97	5.777%	$76.1277	$76.13	$76.15	$76.10
Purchase #6	$202.97	6.259%	$215.6739	$215.67	$215.65	$215.70
Purchase #7	$28.33	10.325%	$31.2551	$31.26	$31.25	$31.30
7 purchase totals =	$648.65		$693.9235	$693.93	$693.90	$693.90