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	$157.92	13.764%	$179.6561	$179.66	$179.65	$179.70
Purchase #2	$139.69	8.820%	$152.0107	$152.01	$152.00	$152.00
Purchase #3	$60.33	11.583%	$67.318	$67.32	$67.30	$67.30
Purchase #4	$189.46	5.321%	$199.5412	$199.54	$199.55	$199.50
Purchase #5	$96.76	9.122%	$105.5864	$105.59	$105.60	$105.60
Purchase #6	$75.31	5.725%	$79.6215	$79.62	$79.60	$79.60
Purchase #7	$138.84	11.707%	$155.094	$155.09	$155.10	$155.10
7 purchase totals =	$858.31		$938.8279	$938.83	$938.80	$938.80