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	$96.90	7.513%	$104.1801	$104.18	$104.20	$104.20
Purchase #2	$135.74	4.313%	$141.5945	$141.59	$141.60	$141.60
Purchase #3	$212.94	3.868%	$221.1765	$221.18	$221.20	$221.20
Purchase #4	$142.93	6.375%	$152.0418	$152.04	$152.05	$152.00
Purchase #5	$28.88	12.846%	$32.5899	$32.59	$32.60	$32.60
Purchase #6	$183.36	9.195%	$200.22	$200.22	$200.20	$200.20
Purchase #7	$136.92	11.514%	$152.685	$152.69	$152.70	$152.70
7 purchase totals =	$937.67		$1,004.4878	$1,004.49	$1,004.55	$1,004.50