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	$98.82	12.446%	$111.1191	$111.12	$111.10	$111.10
Purchase #2	$95.62	4.105%	$99.5452	$99.55	$99.55	$99.50
Purchase #3	$187.28	3.813%	$194.421	$194.42	$194.40	$194.40
Purchase #4	$121.51	8.711%	$132.0947	$132.09	$132.10	$132.10
Purchase #5	$46.63	12.223%	$52.3296	$52.33	$52.35	$52.30
Purchase #6	$125.70	12.400%	$141.2868	$141.29	$141.30	$141.30
Purchase #7	$107.91	5.183%	$113.503	$113.50	$113.50	$113.50
7 purchase totals =	$783.47		$844.2994	$844.30	$844.30	$844.20