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	$158.77	5.441%	$167.4087	$167.41	$167.40	$167.40
Purchase #2	$136.95	12.678%	$154.3125	$154.31	$154.30	$154.30
Purchase #3	$85.79	3.752%	$89.0088	$89.01	$89.00	$89.00
Purchase #4	$67.74	12.414%	$76.1492	$76.15	$76.15	$76.10
Purchase #5	$188.89	13.459%	$214.3127	$214.31	$214.30	$214.30
Purchase #6	$217.86	11.706%	$243.3627	$243.36	$243.35	$243.40
Purchase #7	$174.93	4.248%	$182.361	$182.36	$182.35	$182.40
7 purchase totals =	$1,030.93		$1,126.9156	$1,126.91	$1,126.85	$1,126.90