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	$141.85	6.841%	$151.554	$151.55	$151.55	$151.60
Purchase #2	$99.34	13.761%	$113.0102	$113.01	$113.00	$113.00
Purchase #3	$189.42	9.722%	$207.8354	$207.84	$207.85	$207.80
Purchase #4	$7.61	13.520%	$8.6389	$8.64	$8.65	$8.60
Purchase #5	$75.59	9.693%	$82.9169	$82.92	$82.90	$82.90
Purchase #6	$98.46	9.333%	$107.6493	$107.65	$107.65	$107.60
Purchase #7	$79.94	13.719%	$90.907	$90.91	$90.90	$90.90
7 purchase totals =	$692.21		$762.5117	$762.52	$762.50	$762.40