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	$142.52	6.663%	$152.0161	$152.02	$152.00	$152.00
Purchase #2	$188.46	5.188%	$198.2373	$198.24	$198.25	$198.20
Purchase #3	$113.78	11.598%	$126.9762	$126.98	$127.00	$127.00
Purchase #4	$242.56	9.731%	$266.1635	$266.16	$266.15	$266.20
Purchase #5	$120.46	5.336%	$126.8877	$126.89	$126.90	$126.90
Purchase #6	$245.46	13.509%	$278.6192	$278.62	$278.60	$278.60
Purchase #7	$155.78	6.556%	$165.9929	$165.99	$166.00	$166.00
7 purchase totals =	$1,209.02		$1,314.8929	$1,314.90	$1,314.90	$1,314.90