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	$167.73	6.327%	$178.3423	$178.34	$178.35	$178.30
Purchase #2	$167.62	8.322%	$181.5693	$181.57	$181.55	$181.60
Purchase #3	$199.50	12.567%	$224.5712	$224.57	$224.55	$224.60
Purchase #4	$63.38	13.311%	$71.8165	$71.82	$71.80	$71.80
Purchase #5	$69.79	5.734%	$73.7918	$73.79	$73.80	$73.80
Purchase #6	$199.65	11.410%	$222.4301	$222.43	$222.45	$222.40
Purchase #7	$71.30	13.407%	$80.8592	$80.86	$80.85	$80.90
7 purchase totals =	$938.97		$1,033.3804	$1,033.38	$1,033.35	$1,033.40