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	$170.69	12.218%	$191.5449	$191.54	$191.55	$191.50
Purchase #2	$103.76	5.450%	$109.4149	$109.41	$109.40	$109.40
Purchase #3	$155.89	13.685%	$177.2235	$177.22	$177.20	$177.20
Purchase #4	$222.63	8.751%	$242.1124	$242.11	$242.10	$242.10
Purchase #5	$102.49	9.521%	$112.2481	$112.25	$112.25	$112.20
Purchase #6	$137.37	11.488%	$153.1511	$153.15	$153.15	$153.20
Purchase #7	$143.76	4.570%	$150.3298	$150.33	$150.35	$150.30
7 purchase totals =	$1,036.59		$1,136.0247	$1,136.01	$1,136.00	$1,135.90