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	$69.71	5.571%	$73.5935	$73.59	$73.60	$73.60
Purchase #2	$218.96	4.149%	$228.0447	$228.04	$228.05	$228.00
Purchase #3	$43.81	6.830%	$46.8022	$46.80	$46.80	$46.80
Purchase #4	$76.82	6.874%	$82.1006	$82.10	$82.10	$82.10
Purchase #5	$142.96	4.443%	$149.3117	$149.31	$149.30	$149.30
Purchase #6	$240.50	6.190%	$255.387	$255.39	$255.40	$255.40
Purchase #7	$222.66	11.873%	$249.0964	$249.10	$249.10	$249.10
7 purchase totals =	$1,015.42		$1,084.3361	$1,084.33	$1,084.35	$1,084.30