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	$99.72	6.701%	$106.4022	$106.40	$106.40	$106.40
Purchase #2	$39.82	10.156%	$43.8641	$43.86	$43.85	$43.90
Purchase #3	$6.34	4.797%	$6.6441	$6.64	$6.65	$6.60
Purchase #4	$116.50	9.174%	$127.1877	$127.19	$127.20	$127.20
Purchase #5	$83.42	6.127%	$88.5311	$88.53	$88.55	$88.50
Purchase #6	$64.31	5.380%	$67.7699	$67.77	$67.75	$67.80
Purchase #7	$116.40	9.640%	$127.621	$127.62	$127.60	$127.60
7 purchase totals =	$526.51		$568.0201	$568.01	$568.00	$568.00