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	$80.80	5.147%	$84.9588	$84.96	$84.95	$85.00
Purchase #2	$37.80	9.179%	$41.2697	$41.27	$41.25	$41.30
Purchase #3	$58.84	5.254%	$61.9315	$61.93	$61.95	$61.90
Purchase #4	$181.59	4.653%	$190.0394	$190.04	$190.05	$190.00
Purchase #5	$162.35	11.248%	$180.6111	$180.61	$180.60	$180.60
Purchase #6	$72.52	13.786%	$82.5176	$82.52	$82.50	$82.50
Purchase #7	$204.33	9.283%	$223.298	$223.30	$223.30	$223.30
7 purchase totals =	$798.23		$864.6261	$864.63	$864.60	$864.60