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	$215.34	7.854%	$232.2528	$232.25	$232.25	$232.30
Purchase #2	$243.38	4.649%	$254.6947	$254.69	$254.70	$254.70
Purchase #3	$35.49	9.758%	$38.9531	$38.95	$38.95	$39.00
Purchase #4	$231.34	8.613%	$251.2653	$251.27	$251.25	$251.30
Purchase #5	$82.72	7.831%	$89.1978	$89.20	$89.20	$89.20
Purchase #6	$84.62	5.390%	$89.181	$89.18	$89.20	$89.20
Purchase #7	$56.44	7.402%	$60.6177	$60.62	$60.60	$60.60
7 purchase totals =	$949.33		$1,016.1624	$1,016.16	$1,016.15	$1,016.30