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	$235.91	5.228%	$248.2434	$248.24	$248.25	$248.20
Purchase #2	$171.38	4.187%	$178.5557	$178.56	$178.55	$178.60
Purchase #3	$160.81	4.116%	$167.4289	$167.43	$167.45	$167.40
Purchase #4	$219.94	5.399%	$231.8146	$231.81	$231.80	$231.80
Purchase #5	$74.30	5.460%	$78.3568	$78.36	$78.35	$78.40
Purchase #6	$171.94	11.156%	$191.1216	$191.12	$191.10	$191.10
Purchase #7	$213.28	6.794%	$227.7702	$227.77	$227.75	$227.80
7 purchase totals =	$1,247.56		$1,323.2912	$1,323.29	$1,323.25	$1,323.30