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	$21.86	11.827%	$24.4454	$24.45	$24.45	$24.40
Purchase #2	$216.31	11.282%	$240.7141	$240.71	$240.70	$240.70
Purchase #3	$229.72	8.257%	$248.688	$248.69	$248.70	$248.70
Purchase #4	$188.79	12.550%	$212.4831	$212.48	$212.50	$212.50
Purchase #5	$72.56	10.727%	$80.3435	$80.34	$80.35	$80.30
Purchase #6	$85.69	5.597%	$90.4861	$90.49	$90.50	$90.50
Purchase #7	$184.40	7.322%	$197.9018	$197.90	$197.90	$197.90
7 purchase totals =	$999.33		$1,095.0620	$1,095.06	$1,095.10	$1,095.00