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	$210.45	7.341%	$225.8991	$225.90	$225.90	$225.90
Purchase #2	$64.82	6.312%	$68.9114	$68.91	$68.90	$68.90
Purchase #3	$247.54	9.812%	$271.8286	$271.83	$271.85	$271.80
Purchase #4	$41.98	4.728%	$43.9648	$43.96	$43.95	$44.00
Purchase #5	$194.28	3.107%	$200.3163	$200.32	$200.30	$200.30
Purchase #6	$73.61	12.741%	$82.9887	$82.99	$83.00	$83.00
Purchase #7	$247.86	6.873%	$264.8954	$264.90	$264.90	$264.90
7 purchase totals =	$1,080.54		$1,158.8043	$1,158.81	$1,158.80	$1,158.80