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	$212.96	7.310%	$228.5274	$228.53	$228.55	$228.50
Purchase #2	$226.98	5.428%	$239.3005	$239.30	$239.30	$239.30
Purchase #3	$154.54	13.639%	$175.6177	$175.62	$175.60	$175.60
Purchase #4	$139.87	13.722%	$159.063	$159.06	$159.05	$159.10
Purchase #5	$149.94	4.356%	$156.4714	$156.47	$156.45	$156.50
Purchase #6	$89.92	10.682%	$99.5253	$99.53	$99.55	$99.50
Purchase #7	$214.67	12.871%	$242.3002	$242.30	$242.30	$242.30
7 purchase totals =	$1,188.88		$1,300.8055	$1,300.81	$1,300.80	$1,300.80