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	$178.36	8.136%	$192.8714	$192.87	$192.85	$192.90
Purchase #2	$77.39	4.479%	$80.8563	$80.86	$80.85	$80.90
Purchase #3	$199.69	9.729%	$219.1178	$219.12	$219.10	$219.10
Purchase #4	$182.90	9.738%	$200.7108	$200.71	$200.70	$200.70
Purchase #5	$250.72	6.627%	$267.3352	$267.34	$267.35	$267.30
Purchase #6	$37.49	12.318%	$42.108	$42.11	$42.10	$42.10
Purchase #7	$245.80	13.760%	$279.6221	$279.62	$279.60	$279.60
7 purchase totals =	$1,172.35		$1,282.6216	$1,282.63	$1,282.55	$1,282.60