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	$76.52	7.310%	$82.1136	$82.11	$82.10	$82.10
Purchase #2	$116.77	12.309%	$131.1432	$131.14	$131.15	$131.10
Purchase #3	$213.69	6.359%	$227.2785	$227.28	$227.30	$227.30
Purchase #4	$122.47	3.613%	$126.8948	$126.89	$126.90	$126.90
Purchase #5	$69.63	13.620%	$79.1136	$79.11	$79.10	$79.10
Purchase #6	$208.26	5.728%	$220.1891	$220.19	$220.20	$220.20
Purchase #7	$198.33	10.681%	$219.5136	$219.51	$219.50	$219.50
7 purchase totals =	$1,005.67		$1,086.2464	$1,086.23	$1,086.25	$1,086.20