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	$178.92	3.768%	$185.6617	$185.66	$185.65	$185.70
Purchase #2	$154.87	11.214%	$172.2371	$172.24	$172.25	$172.20
Purchase #3	$36.30	4.255%	$37.8446	$37.84	$37.85	$37.80
Purchase #4	$71.56	9.711%	$78.5092	$78.51	$78.50	$78.50
Purchase #5	$114.81	6.727%	$122.5333	$122.53	$122.55	$122.50
Purchase #6	$221.44	7.210%	$237.4058	$237.41	$237.40	$237.40
Purchase #7	$226.78	3.162%	$233.9508	$233.95	$233.95	$234.00
7 purchase totals =	$1,004.68		$1,068.1425	$1,068.14	$1,068.15	$1,068.10