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	$59.74	13.786%	$67.9758	$67.98	$68.00	$68.00
Purchase #2	$161.84	11.279%	$180.0939	$180.09	$180.10	$180.10
Purchase #3	$174.76	10.614%	$193.309	$193.31	$193.30	$193.30
Purchase #4	$176.31	11.426%	$196.4552	$196.46	$196.45	$196.50
Purchase #5	$43.50	4.379%	$45.4049	$45.40	$45.40	$45.40
Purchase #6	$199.98	10.454%	$220.8859	$220.89	$220.90	$220.90
Purchase #7	$135.47	4.574%	$141.6664	$141.67	$141.65	$141.70
7 purchase totals =	$951.60		$1,045.7911	$1,045.80	$1,045.80	$1,045.90