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	$136.74	11.770%	$152.8343	$152.83	$152.85	$152.80
Purchase #2	$148.97	4.134%	$155.1284	$155.13	$155.15	$155.10
Purchase #3	$43.89	12.373%	$49.3205	$49.32	$49.30	$49.30
Purchase #4	$171.39	8.676%	$186.2598	$186.26	$186.25	$186.30
Purchase #5	$204.59	7.500%	$219.9343	$219.93	$219.95	$219.90
Purchase #6	$90.61	13.487%	$102.8306	$102.83	$102.85	$102.80
Purchase #7	$78.70	12.740%	$88.7264	$88.73	$88.75	$88.70
7 purchase totals =	$874.89		$955.0343	$955.03	$955.10	$954.90