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	$74.50	10.102%	$82.026	$82.03	$82.05	$82.00
Purchase #2	$76.64	10.710%	$84.8481	$84.85	$84.85	$84.80
Purchase #3	$18.75	12.340%	$21.0638	$21.06	$21.05	$21.10
Purchase #4	$48.34	13.346%	$54.7915	$54.79	$54.80	$54.80
Purchase #5	$6.38	12.231%	$7.1603	$7.16	$7.15	$7.20
Purchase #6	$116.56	12.474%	$131.0997	$131.10	$131.10	$131.10
Purchase #7	$225.77	3.254%	$233.1166	$233.12	$233.10	$233.10
7 purchase totals =	$566.94		$614.1060	$614.11	$614.10	$614.10