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	$180.81	5.818%	$191.3295	$191.33	$191.35	$191.30
Purchase #2	$104.46	9.313%	$114.1884	$114.19	$114.20	$114.20
Purchase #3	$34.81	10.287%	$38.3909	$38.39	$38.40	$38.40
Purchase #4	$175.55	5.665%	$185.4949	$185.49	$185.50	$185.50
Purchase #5	$172.78	3.787%	$179.3232	$179.32	$179.30	$179.30
Purchase #6	$94.64	13.263%	$107.1921	$107.19	$107.20	$107.20
Purchase #7	$30.53	6.233%	$32.4329	$32.43	$32.45	$32.40
7 purchase totals =	$793.58		$848.3519	$848.34	$848.40	$848.30