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	$110.72	7.120%	$118.6033	$118.60	$118.60	$118.60
Purchase #2	$180.93	8.789%	$196.8319	$196.83	$196.85	$196.80
Purchase #3	$88.73	4.275%	$92.5232	$92.52	$92.50	$92.50
Purchase #4	$155.98	4.156%	$162.4625	$162.46	$162.45	$162.50
Purchase #5	$236.59	11.769%	$264.4343	$264.43	$264.45	$264.40
Purchase #6	$143.58	3.831%	$149.0805	$149.08	$149.10	$149.10
Purchase #7	$35.45	10.418%	$39.1432	$39.14	$39.15	$39.10
7 purchase totals =	$951.98		$1,023.0789	$1,023.06	$1,023.10	$1,023.00