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	$106.93	8.689%	$116.2211	$116.22	$116.20	$116.20
Purchase #2	$109.27	9.712%	$119.8823	$119.88	$119.90	$119.90
Purchase #3	$170.99	7.610%	$184.0023	$184.00	$184.00	$184.00
Purchase #4	$6.73	8.749%	$7.3188	$7.32	$7.30	$7.30
Purchase #5	$188.88	9.271%	$206.3911	$206.39	$206.40	$206.40
Purchase #6	$165.79	3.840%	$172.1563	$172.16	$172.15	$172.20
Purchase #7	$185.78	5.765%	$196.4902	$196.49	$196.50	$196.50
7 purchase totals =	$934.37		$1,002.4621	$1,002.46	$1,002.45	$1,002.50