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	$112.75	9.508%	$123.4703	$123.47	$123.45	$123.50
Purchase #2	$229.80	4.266%	$239.6033	$239.60	$239.60	$239.60
Purchase #3	$56.40	4.814%	$59.1151	$59.12	$59.10	$59.10
Purchase #4	$29.52	3.518%	$30.5585	$30.56	$30.55	$30.60
Purchase #5	$222.84	9.851%	$244.792	$244.79	$244.80	$244.80
Purchase #6	$89.78	10.153%	$98.8954	$98.90	$98.90	$98.90
Purchase #7	$242.65	10.615%	$268.4073	$268.41	$268.40	$268.40
7 purchase totals =	$983.74		$1,064.8419	$1,064.85	$1,064.80	$1,064.90