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	$194.38	9.251%	$212.3621	$212.36	$212.35	$212.40
Purchase #2	$39.51	4.843%	$41.4235	$41.42	$41.40	$41.40
Purchase #3	$218.56	10.744%	$242.0421	$242.04	$242.05	$242.00
Purchase #4	$224.43	7.161%	$240.5014	$240.50	$240.50	$240.50
Purchase #5	$68.59	3.194%	$70.7808	$70.78	$70.80	$70.80
Purchase #6	$170.42	9.413%	$186.4616	$186.46	$186.45	$186.50
Purchase #7	$74.98	10.181%	$82.6137	$82.61	$82.60	$82.60
7 purchase totals =	$990.87		$1,076.1852	$1,076.17	$1,076.15	$1,076.20