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	$207.31	12.792%	$233.8291	$233.83	$233.85	$233.80
Purchase #2	$230.40	3.152%	$237.6622	$237.66	$237.65	$237.70
Purchase #3	$236.82	13.345%	$268.4236	$268.42	$268.40	$268.40
Purchase #4	$5.76	5.764%	$6.092	$6.09	$6.10	$6.10
Purchase #5	$106.33	11.132%	$118.1667	$118.17	$118.15	$118.20
Purchase #6	$120.87	8.682%	$131.3639	$131.36	$131.35	$131.40
Purchase #7	$53.33	12.322%	$59.9013	$59.90	$59.90	$59.90
7 purchase totals =	$960.82		$1,055.4388	$1,055.43	$1,055.40	$1,055.50