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	$165.27	9.423%	$180.8434	$180.84	$180.85	$180.80
Purchase #2	$41.93	6.806%	$44.7838	$44.78	$44.80	$44.80
Purchase #3	$35.78	7.621%	$38.5068	$38.51	$38.50	$38.50
Purchase #4	$151.96	12.681%	$171.23	$171.23	$171.25	$171.20
Purchase #5	$193.76	8.679%	$210.5764	$210.58	$210.60	$210.60
Purchase #6	$136.83	6.170%	$145.2724	$145.27	$145.25	$145.30
Purchase #7	$223.75	13.606%	$254.1934	$254.19	$254.20	$254.20
7 purchase totals =	$949.28		$1,045.4062	$1,045.40	$1,045.45	$1,045.40