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	$196.89	6.551%	$209.7883	$209.79	$209.80	$209.80
Purchase #2	$126.33	5.289%	$133.0116	$133.01	$133.00	$133.00
Purchase #3	$202.27	9.720%	$221.9306	$221.93	$221.95	$221.90
Purchase #4	$70.29	12.149%	$78.8295	$78.83	$78.85	$78.80
Purchase #5	$196.59	11.305%	$218.8145	$218.81	$218.80	$218.80
Purchase #6	$44.59	6.433%	$47.4585	$47.46	$47.45	$47.50
Purchase #7	$17.91	13.803%	$20.3821	$20.38	$20.40	$20.40
7 purchase totals =	$854.87		$930.2151	$930.21	$930.25	$930.20