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	$143.81	9.510%	$157.4863	$157.49	$157.50	$157.50
Purchase #2	$22.51	11.404%	$25.077	$25.08	$25.10	$25.10
Purchase #3	$91.28	9.790%	$100.2163	$100.22	$100.20	$100.20
Purchase #4	$171.94	11.578%	$191.8472	$191.85	$191.85	$191.80
Purchase #5	$130.37	8.649%	$141.6457	$141.65	$141.65	$141.60
Purchase #6	$223.66	11.191%	$248.6898	$248.69	$248.70	$248.70
Purchase #7	$142.26	10.305%	$156.9199	$156.92	$156.90	$156.90
7 purchase totals =	$925.83		$1,021.8822	$1,021.90	$1,021.90	$1,021.80