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	$85.50	13.812%	$97.3093	$97.31	$97.30	$97.30
Purchase #2	$166.45	11.155%	$185.0175	$185.02	$185.00	$185.00
Purchase #3	$106.80	10.630%	$118.1528	$118.15	$118.15	$118.20
Purchase #4	$53.25	3.117%	$54.9098	$54.91	$54.90	$54.90
Purchase #5	$128.79	10.279%	$142.0283	$142.03	$142.05	$142.00
Purchase #6	$213.40	6.811%	$227.9347	$227.93	$227.95	$227.90
Purchase #7	$221.92	6.487%	$236.316	$236.32	$236.30	$236.30
7 purchase totals =	$976.11		$1,061.6684	$1,061.67	$1,061.65	$1,061.60