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	$216.77	10.369%	$239.2469	$239.25	$239.25	$239.20
Purchase #2	$235.81	8.368%	$255.5426	$255.54	$255.55	$255.50
Purchase #3	$98.43	12.818%	$111.0468	$111.05	$111.05	$111.00
Purchase #4	$245.87	13.415%	$278.8535	$278.85	$278.85	$278.90
Purchase #5	$64.56	8.322%	$69.9327	$69.93	$69.95	$69.90
Purchase #6	$191.31	11.740%	$213.7698	$213.77	$213.75	$213.80
Purchase #7	$114.88	7.441%	$123.4282	$123.43	$123.45	$123.40
7 purchase totals =	$1,167.63		$1,291.8205	$1,291.82	$1,291.85	$1,291.70