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	$100.86	3.364%	$104.2529	$104.25	$104.25	$104.30
Purchase #2	$201.58	8.852%	$219.4239	$219.42	$219.40	$219.40
Purchase #3	$36.67	5.558%	$38.7081	$38.71	$38.70	$38.70
Purchase #4	$102.69	6.664%	$109.5333	$109.53	$109.55	$109.50
Purchase #5	$80.34	3.330%	$83.0153	$83.02	$83.00	$83.00
Purchase #6	$163.77	12.736%	$184.6277	$184.63	$184.65	$184.60
Purchase #7	$187.55	4.793%	$196.5393	$196.54	$196.55	$196.50
7 purchase totals =	$873.46		$936.1005	$936.10	$936.10	$936.00