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	$154.93	6.854%	$165.5489	$165.55	$165.55	$165.50
Purchase #2	$205.87	11.397%	$229.333	$229.33	$229.35	$229.30
Purchase #3	$23.44	10.667%	$25.9403	$25.94	$25.95	$25.90
Purchase #4	$228.34	10.410%	$252.1102	$252.11	$252.10	$252.10
Purchase #5	$101.89	9.818%	$111.8936	$111.89	$111.90	$111.90
Purchase #6	$114.93	7.820%	$123.9175	$123.92	$123.90	$123.90
Purchase #7	$211.27	5.315%	$222.499	$222.50	$222.50	$222.50
7 purchase totals =	$1,040.67		$1,131.2425	$1,131.24	$1,131.25	$1,131.10