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	$227.49	9.283%	$248.6079	$248.61	$248.60	$248.60
Purchase #2	$91.57	7.196%	$98.1594	$98.16	$98.15	$98.20
Purchase #3	$128.95	9.769%	$141.5471	$141.55	$141.55	$141.50
Purchase #4	$184.89	4.341%	$192.9161	$192.92	$192.90	$192.90
Purchase #5	$134.25	13.645%	$152.5684	$152.57	$152.55	$152.60
Purchase #6	$120.55	6.259%	$128.0952	$128.10	$128.10	$128.10
Purchase #7	$212.87	6.820%	$227.3877	$227.39	$227.40	$227.40
7 purchase totals =	$1,100.57		$1,189.2818	$1,189.30	$1,189.25	$1,189.30