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	$130.70	10.823%	$144.8457	$144.85	$144.85	$144.80
Purchase #2	$40.55	5.123%	$42.6274	$42.63	$42.65	$42.60
Purchase #3	$220.36	5.866%	$233.2863	$233.29	$233.30	$233.30
Purchase #4	$98.32	11.694%	$109.8175	$109.82	$109.80	$109.80
Purchase #5	$133.74	6.482%	$142.409	$142.41	$142.40	$142.40
Purchase #6	$163.87	7.464%	$176.1013	$176.10	$176.10	$176.10
Purchase #7	$123.79	7.467%	$133.0334	$133.03	$133.05	$133.00
7 purchase totals =	$911.33		$982.1206	$982.13	$982.15	$982.00