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	$41.27	5.673%	$43.6112	$43.61	$43.60	$43.60
Purchase #2	$73.62	7.682%	$79.2755	$79.28	$79.30	$79.30
Purchase #3	$71.92	5.825%	$76.1093	$76.11	$76.10	$76.10
Purchase #4	$49.38	4.524%	$51.614	$51.61	$51.60	$51.60
Purchase #5	$22.94	3.802%	$23.8122	$23.81	$23.80	$23.80
Purchase #6	$94.56	10.105%	$104.1153	$104.12	$104.10	$104.10
Purchase #7	$93.82	7.234%	$100.6069	$100.61	$100.60	$100.60
7 purchase totals =	$447.51		$479.1444	$479.15	$479.10	$479.10