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	$119.98	9.570%	$131.4621	$131.46	$131.45	$131.50
Purchase #2	$17.74	7.786%	$19.1212	$19.12	$19.10	$19.10
Purchase #3	$89.73	11.746%	$100.2697	$100.27	$100.25	$100.30
Purchase #4	$25.87	9.334%	$28.2847	$28.28	$28.30	$28.30
Purchase #5	$172.42	7.117%	$184.6911	$184.69	$184.70	$184.70
Purchase #6	$198.70	11.807%	$222.1605	$222.16	$222.15	$222.20
Purchase #7	$73.64	3.701%	$76.3654	$76.37	$76.35	$76.40
7 purchase totals =	$698.08		$762.3547	$762.35	$762.30	$762.50