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	$222.39	10.405%	$245.5297	$245.53	$245.55	$245.50
Purchase #2	$37.75	7.616%	$40.625	$40.63	$40.65	$40.60
Purchase #3	$220.30	12.772%	$248.4367	$248.44	$248.45	$248.40
Purchase #4	$238.61	11.193%	$265.3176	$265.32	$265.30	$265.30
Purchase #5	$170.85	4.808%	$179.0645	$179.06	$179.05	$179.10
Purchase #6	$211.32	4.323%	$220.4554	$220.46	$220.45	$220.50
Purchase #7	$78.28	6.748%	$83.5623	$83.56	$83.55	$83.60
7 purchase totals =	$1,179.50		$1,282.9912	$1,283.00	$1,283.00	$1,283.00