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	$240.71	6.317%	$255.9157	$255.92	$255.90	$255.90
Purchase #2	$73.54	5.132%	$77.3141	$77.31	$77.30	$77.30
Purchase #3	$157.60	8.835%	$171.524	$171.52	$171.50	$171.50
Purchase #4	$57.40	3.317%	$59.304	$59.30	$59.30	$59.30
Purchase #5	$229.70	11.118%	$255.238	$255.24	$255.25	$255.20
Purchase #6	$40.39	11.669%	$45.1031	$45.10	$45.10	$45.10
Purchase #7	$179.97	4.186%	$187.5035	$187.50	$187.50	$187.50
7 purchase totals =	$979.31		$1,051.9024	$1,051.89	$1,051.85	$1,051.80