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	$172.69	9.632%	$189.3235	$189.32	$189.30	$189.30
Purchase #2	$30.96	3.439%	$32.0247	$32.02	$32.00	$32.00
Purchase #3	$220.38	11.679%	$246.1182	$246.12	$246.10	$246.10
Purchase #4	$15.48	12.448%	$17.407	$17.41	$17.40	$17.40
Purchase #5	$208.86	6.226%	$221.8636	$221.86	$221.85	$221.90
Purchase #6	$143.29	13.632%	$162.8233	$162.82	$162.80	$162.80
Purchase #7	$131.59	10.742%	$145.7254	$145.73	$145.75	$145.70
7 purchase totals =	$923.25		$1,015.2857	$1,015.28	$1,015.20	$1,015.20