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	$173.32	10.388%	$191.3245	$191.32	$191.30	$191.30
Purchase #2	$48.39	6.459%	$51.5155	$51.52	$51.50	$51.50
Purchase #3	$64.78	6.285%	$68.8514	$68.85	$68.85	$68.90
Purchase #4	$79.56	11.630%	$88.8128	$88.81	$88.80	$88.80
Purchase #5	$160.37	8.597%	$174.157	$174.16	$174.15	$174.20
Purchase #6	$216.86	11.437%	$241.6623	$241.66	$241.65	$241.70
Purchase #7	$247.50	13.210%	$280.1948	$280.19	$280.20	$280.20
7 purchase totals =	$990.78		$1,096.5183	$1,096.51	$1,096.45	$1,096.60