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	$38.39	6.416%	$40.8531	$40.85	$40.85	$40.90
Purchase #2	$91.35	4.616%	$95.5667	$95.57	$95.55	$95.60
Purchase #3	$211.66	8.584%	$229.8289	$229.83	$229.85	$229.80
Purchase #4	$59.26	4.421%	$61.8799	$61.88	$61.90	$61.90
Purchase #5	$127.28	7.599%	$136.952	$136.95	$136.95	$137.00
Purchase #6	$151.95	11.639%	$169.6355	$169.64	$169.65	$169.60
Purchase #7	$138.41	11.134%	$153.8206	$153.82	$153.80	$153.80
7 purchase totals =	$818.30		$888.5367	$888.54	$888.55	$888.60