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	$116.63	11.423%	$129.9526	$129.95	$129.95	$130.00
Purchase #2	$174.26	12.846%	$196.6454	$196.65	$196.65	$196.60
Purchase #3	$123.99	5.222%	$130.4648	$130.46	$130.45	$130.50
Purchase #4	$215.82	4.307%	$225.1154	$225.12	$225.10	$225.10
Purchase #5	$36.96	4.287%	$38.5445	$38.54	$38.55	$38.50
Purchase #6	$48.89	3.380%	$50.5425	$50.54	$50.55	$50.50
Purchase #7	$12.65	3.416%	$13.0821	$13.08	$13.10	$13.10
7 purchase totals =	$729.20		$784.3473	$784.34	$784.35	$784.30