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	$190.77	4.616%	$199.5759	$199.58	$199.60	$199.60
Purchase #2	$66.63	6.397%	$70.8923	$70.89	$70.90	$70.90
Purchase #3	$183.27	3.289%	$189.2978	$189.30	$189.30	$189.30
Purchase #4	$139.62	10.791%	$154.6864	$154.69	$154.70	$154.70
Purchase #5	$238.37	11.563%	$265.9327	$265.93	$265.95	$265.90
Purchase #6	$38.53	13.279%	$43.6464	$43.65	$43.65	$43.60
Purchase #7	$169.64	7.170%	$181.8032	$181.80	$181.80	$181.80
7 purchase totals =	$1,026.83		$1,105.8347	$1,105.84	$1,105.90	$1,105.80