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	$123.77	3.106%	$127.6143	$127.61	$127.60	$127.60
Purchase #2	$141.66	8.711%	$154	$154.00	$154.00	$154.00
Purchase #3	$8.94	10.686%	$9.8953	$9.90	$9.90	$9.90
Purchase #4	$35.54	3.196%	$36.6759	$36.68	$36.70	$36.70
Purchase #5	$115.74	6.527%	$123.2943	$123.29	$123.30	$123.30
Purchase #6	$54.41	9.323%	$59.4826	$59.48	$59.50	$59.50
Purchase #7	$58.62	11.564%	$65.3988	$65.40	$65.40	$65.40
7 purchase totals =	$538.68		$576.3612	$576.36	$576.40	$576.40