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	$57.40	6.456%	$61.1057	$61.11	$61.10	$61.10
Purchase #2	$246.94	7.113%	$264.5048	$264.50	$264.50	$264.50
Purchase #3	$67.61	7.775%	$72.8667	$72.87	$72.85	$72.90
Purchase #4	$171.25	6.427%	$182.2562	$182.26	$182.25	$182.30
Purchase #5	$8.63	8.139%	$9.3324	$9.33	$9.35	$9.30
Purchase #6	$210.60	5.767%	$222.7453	$222.75	$222.75	$222.70
Purchase #7	$98.26	11.782%	$109.837	$109.84	$109.85	$109.80
7 purchase totals =	$860.69		$922.6481	$922.66	$922.65	$922.60