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	$153.65	11.309%	$171.0263	$171.03	$171.05	$171.00
Purchase #2	$161.85	12.220%	$181.6281	$181.63	$181.65	$181.60
Purchase #3	$141.36	9.424%	$154.6818	$154.68	$154.70	$154.70
Purchase #4	$123.82	3.484%	$128.1339	$128.13	$128.15	$128.10
Purchase #5	$149.55	9.683%	$164.0309	$164.03	$164.05	$164.00
Purchase #6	$184.54	13.858%	$210.1136	$210.11	$210.10	$210.10
Purchase #7	$64.58	11.301%	$71.8782	$71.88	$71.90	$71.90
7 purchase totals =	$979.35		$1,081.4928	$1,081.49	$1,081.60	$1,081.40