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	$109.83	6.323%	$116.7746	$116.77	$116.75	$116.80
Purchase #2	$109.31	11.736%	$122.1386	$122.14	$122.15	$122.10
Purchase #3	$118.85	5.737%	$125.6684	$125.67	$125.65	$125.70
Purchase #4	$219.97	10.146%	$242.2882	$242.29	$242.30	$242.30
Purchase #5	$188.97	4.122%	$196.7593	$196.76	$196.75	$196.80
Purchase #6	$69.83	3.689%	$72.406	$72.41	$72.40	$72.40
Purchase #7	$204.89	4.660%	$214.4379	$214.44	$214.45	$214.40
7 purchase totals =	$1,021.65		$1,090.4730	$1,090.48	$1,090.45	$1,090.50