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	$104.73	8.176%	$113.2927	$113.29	$113.30	$113.30
Purchase #2	$78.40	6.152%	$83.2232	$83.22	$83.20	$83.20
Purchase #3	$86.69	6.378%	$92.2191	$92.22	$92.20	$92.20
Purchase #4	$170.37	6.411%	$181.2924	$181.29	$181.30	$181.30
Purchase #5	$104.33	5.324%	$109.8845	$109.88	$109.90	$109.90
Purchase #6	$197.32	12.165%	$221.324	$221.32	$221.30	$221.30
Purchase #7	$31.89	5.530%	$33.6535	$33.65	$33.65	$33.70
7 purchase totals =	$773.73		$834.8894	$834.87	$834.85	$834.90