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	$192.48	11.826%	$215.2427	$215.24	$215.25	$215.20
Purchase #2	$108.80	13.582%	$123.5772	$123.58	$123.60	$123.60
Purchase #3	$172.82	7.204%	$185.27	$185.27	$185.25	$185.30
Purchase #4	$73.78	4.767%	$77.2971	$77.30	$77.30	$77.30
Purchase #5	$96.86	11.481%	$107.9805	$107.98	$108.00	$108.00
Purchase #6	$162.60	3.766%	$168.7235	$168.72	$168.70	$168.70
Purchase #7	$122.95	7.461%	$132.1233	$132.12	$132.10	$132.10
7 purchase totals =	$930.29		$1,010.2143	$1,010.21	$1,010.20	$1,010.20