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	$133.33	10.168%	$146.887	$146.89	$146.90	$146.90
Purchase #2	$82.31	5.454%	$86.7992	$86.80	$86.80	$86.80
Purchase #3	$145.39	11.372%	$161.9238	$161.92	$161.90	$161.90
Purchase #4	$168.90	13.405%	$191.541	$191.54	$191.55	$191.50
Purchase #5	$169.48	4.234%	$176.6558	$176.66	$176.65	$176.70
Purchase #6	$103.28	6.396%	$109.8858	$109.89	$109.90	$109.90
Purchase #7	$146.50	5.226%	$154.1561	$154.16	$154.15	$154.20
7 purchase totals =	$949.19		$1,027.8487	$1,027.86	$1,027.85	$1,027.90