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	$14.40	3.607%	$14.9194	$14.92	$14.90	$14.90
Purchase #2	$82.51	7.262%	$88.5019	$88.50	$88.50	$88.50
Purchase #3	$80.34	6.846%	$85.8401	$85.84	$85.85	$85.80
Purchase #4	$31.38	4.346%	$32.7438	$32.74	$32.75	$32.70
Purchase #5	$55.70	11.117%	$61.8922	$61.89	$61.90	$61.90
Purchase #6	$188.77	13.673%	$214.5805	$214.58	$214.60	$214.60
Purchase #7	$162.50	7.765%	$175.1181	$175.12	$175.10	$175.10
7 purchase totals =	$615.60		$673.5960	$673.59	$673.60	$673.50