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	$42.53	3.791%	$44.1423	$44.14	$44.15	$44.10
Purchase #2	$240.58	11.635%	$268.5715	$268.57	$268.55	$268.60
Purchase #3	$89.87	11.840%	$100.5106	$100.51	$100.50	$100.50
Purchase #4	$204.81	6.459%	$218.0387	$218.04	$218.05	$218.00
Purchase #5	$193.54	3.684%	$200.67	$200.67	$200.65	$200.70
Purchase #6	$226.33	7.772%	$243.9204	$243.92	$243.90	$243.90
Purchase #7	$19.49	7.742%	$20.9989	$21.00	$21.00	$21.00
7 purchase totals =	$1,017.15		$1,096.8524	$1,096.85	$1,096.80	$1,096.80