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	$169.87	3.155%	$175.2294	$175.23	$175.25	$175.20
Purchase #2	$18.64	11.326%	$20.7512	$20.75	$20.75	$20.80
Purchase #3	$150.69	7.463%	$161.936	$161.94	$161.95	$161.90
Purchase #4	$30.72	6.141%	$32.6065	$32.61	$32.60	$32.60
Purchase #5	$128.52	3.134%	$132.5478	$132.55	$132.55	$132.50
Purchase #6	$229.64	10.362%	$253.4353	$253.44	$253.45	$253.40
Purchase #7	$165.25	8.649%	$179.5425	$179.54	$179.55	$179.50
7 purchase totals =	$893.33		$956.0487	$956.06	$956.10	$955.90