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	$75.71	8.817%	$82.3854	$82.39	$82.40	$82.40
Purchase #2	$188.59	11.790%	$210.8248	$210.82	$210.80	$210.80
Purchase #3	$64.94	10.168%	$71.5431	$71.54	$71.55	$71.50
Purchase #4	$181.88	3.668%	$188.5514	$188.55	$188.55	$188.60
Purchase #5	$185.67	10.845%	$205.8059	$205.81	$205.80	$205.80
Purchase #6	$177.59	3.489%	$183.7861	$183.79	$183.80	$183.80
Purchase #7	$123.89	3.432%	$128.1419	$128.14	$128.15	$128.10
7 purchase totals =	$998.27		$1,071.0386	$1,071.04	$1,071.05	$1,071.00