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	$42.94	7.129%	$46.0012	$46.00	$46.00	$46.00
Purchase #2	$37.60	8.636%	$40.8471	$40.85	$40.85	$40.80
Purchase #3	$39.99	9.208%	$43.6723	$43.67	$43.65	$43.70
Purchase #4	$53.83	6.649%	$57.4092	$57.41	$57.40	$57.40
Purchase #5	$120.39	8.628%	$130.7772	$130.78	$130.80	$130.80
Purchase #6	$29.63	5.565%	$31.2789	$31.28	$31.30	$31.30
Purchase #7	$56.96	5.527%	$60.1082	$60.11	$60.10	$60.10
7 purchase totals =	$381.34		$410.0941	$410.10	$410.10	$410.10