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	$100.54	4.196%	$104.7587	$104.76	$104.75	$104.80
Purchase #2	$232.32	6.649%	$247.767	$247.77	$247.75	$247.80
Purchase #3	$223.35	9.582%	$244.7514	$244.75	$244.75	$244.80
Purchase #4	$143.83	13.190%	$162.8012	$162.80	$162.80	$162.80
Purchase #5	$40.91	5.824%	$43.2926	$43.29	$43.30	$43.30
Purchase #6	$215.52	13.277%	$244.1346	$244.13	$244.15	$244.10
Purchase #7	$57.84	10.328%	$63.8137	$63.81	$63.80	$63.80
7 purchase totals =	$1,014.31		$1,111.3192	$1,111.31	$1,111.30	$1,111.40