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	$168.62	11.738%	$188.4126	$188.41	$188.40	$188.40
Purchase #2	$58.32	10.764%	$64.5976	$64.60	$64.60	$64.60
Purchase #3	$62.59	13.403%	$70.9789	$70.98	$71.00	$71.00
Purchase #4	$6.31	8.794%	$6.8649	$6.86	$6.85	$6.90
Purchase #5	$184.50	11.592%	$205.8872	$205.89	$205.90	$205.90
Purchase #6	$162.70	11.160%	$180.8573	$180.86	$180.85	$180.90
Purchase #7	$40.74	3.427%	$42.1362	$42.14	$42.15	$42.10
7 purchase totals =	$683.78		$759.7347	$759.74	$759.75	$759.80