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	$211.58	5.139%	$222.4531	$222.45	$222.45	$222.50
Purchase #2	$91.64	10.502%	$101.264	$101.26	$101.25	$101.30
Purchase #3	$177.70	3.568%	$184.0403	$184.04	$184.05	$184.00
Purchase #4	$75.65	10.131%	$83.3141	$83.31	$83.30	$83.30
Purchase #5	$83.79	7.358%	$89.9553	$89.96	$89.95	$90.00
Purchase #6	$240.98	12.330%	$270.6928	$270.69	$270.70	$270.70
Purchase #7	$142.38	13.261%	$161.261	$161.26	$161.25	$161.30
7 purchase totals =	$1,023.72		$1,112.9806	$1,112.97	$1,112.95	$1,113.10