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	$113.88	8.137%	$123.1464	$123.15	$123.15	$123.10
Purchase #2	$151.51	13.345%	$171.729	$171.73	$171.75	$171.70
Purchase #3	$224.69	11.524%	$250.5833	$250.58	$250.60	$250.60
Purchase #4	$163.96	5.488%	$172.9581	$172.96	$172.95	$173.00
Purchase #5	$76.90	11.802%	$85.9757	$85.98	$86.00	$86.00
Purchase #6	$227.59	4.250%	$237.2626	$237.26	$237.25	$237.30
Purchase #7	$7.68	11.643%	$8.5742	$8.57	$8.55	$8.60
7 purchase totals =	$966.21		$1,050.2293	$1,050.23	$1,050.25	$1,050.30