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	$181.82	12.326%	$204.2311	$204.23	$204.25	$204.20
Purchase #2	$14.48	3.756%	$15.0239	$15.02	$15.00	$15.00
Purchase #3	$184.36	6.565%	$196.4632	$196.46	$196.45	$196.50
Purchase #4	$74.97	10.257%	$82.6597	$82.66	$82.65	$82.70
Purchase #5	$114.71	7.448%	$123.2536	$123.25	$123.25	$123.30
Purchase #6	$85.44	12.872%	$96.4378	$96.44	$96.45	$96.40
Purchase #7	$97.38	11.664%	$108.7384	$108.74	$108.75	$108.70
7 purchase totals =	$753.16		$826.8077	$826.80	$826.80	$826.80