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	$152.73	12.738%	$172.1847	$172.18	$172.20	$172.20
Purchase #2	$109.25	12.820%	$123.2559	$123.26	$123.25	$123.30
Purchase #3	$142.48	13.597%	$161.853	$161.85	$161.85	$161.90
Purchase #4	$138.56	8.569%	$150.4332	$150.43	$150.45	$150.40
Purchase #5	$74.82	8.507%	$81.1849	$81.18	$81.20	$81.20
Purchase #6	$87.66	5.703%	$92.6592	$92.66	$92.65	$92.70
Purchase #7	$218.75	4.814%	$229.2806	$229.28	$229.30	$229.30
7 purchase totals =	$924.25		$1,010.8515	$1,010.84	$1,010.90	$1,011.00