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	$183.52	5.685%	$193.9531	$193.95	$193.95	$194.00
Purchase #2	$98.67	6.457%	$105.0411	$105.04	$105.05	$105.00
Purchase #3	$82.86	7.535%	$89.1035	$89.10	$89.10	$89.10
Purchase #4	$62.40	4.141%	$64.984	$64.98	$65.00	$65.00
Purchase #5	$67.35	8.184%	$72.8619	$72.86	$72.85	$72.90
Purchase #6	$142.49	4.315%	$148.6384	$148.64	$148.65	$148.60
Purchase #7	$72.56	3.133%	$74.8333	$74.83	$74.85	$74.80
7 purchase totals =	$709.85		$749.4153	$749.40	$749.45	$749.40