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	$26.95	4.513%	$28.1663	$28.17	$28.15	$28.20
Purchase #2	$243.41	12.352%	$273.476	$273.48	$273.50	$273.50
Purchase #3	$103.90	9.413%	$113.6801	$113.68	$113.70	$113.70
Purchase #4	$73.61	7.169%	$78.8871	$78.89	$78.90	$78.90
Purchase #5	$70.39	13.459%	$79.8638	$79.86	$79.85	$79.90
Purchase #6	$216.61	4.692%	$226.7733	$226.77	$226.75	$226.80
Purchase #7	$25.28	10.287%	$27.8806	$27.88	$27.90	$27.90
7 purchase totals =	$760.15		$828.7272	$828.73	$828.75	$828.90