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	$111.61	10.463%	$123.2878	$123.29	$123.30	$123.30
Purchase #2	$244.31	7.706%	$263.1365	$263.14	$263.15	$263.10
Purchase #3	$165.84	9.549%	$181.6761	$181.68	$181.70	$181.70
Purchase #4	$5.55	7.867%	$5.9866	$5.99	$6.00	$6.00
Purchase #5	$107.59	3.194%	$111.0264	$111.03	$111.05	$111.00
Purchase #6	$142.86	5.576%	$150.8259	$150.83	$150.85	$150.80
Purchase #7	$89.80	12.417%	$100.9505	$100.95	$100.95	$101.00
7 purchase totals =	$867.56		$936.8898	$936.91	$937.00	$936.90