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	$169.89	8.638%	$184.5651	$184.57	$184.55	$184.60
Purchase #2	$141.55	7.849%	$152.6603	$152.66	$152.65	$152.70
Purchase #3	$46.85	12.777%	$52.836	$52.84	$52.85	$52.80
Purchase #4	$95.92	3.692%	$99.4614	$99.46	$99.45	$99.50
Purchase #5	$80.99	9.710%	$88.8541	$88.85	$88.85	$88.90
Purchase #6	$140.53	12.673%	$158.3394	$158.34	$158.35	$158.30
Purchase #7	$49.37	12.264%	$55.4247	$55.42	$55.40	$55.40
7 purchase totals =	$725.10		$792.1410	$792.14	$792.10	$792.20