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	$107.89	5.234%	$113.537	$113.54	$113.55	$113.50
Purchase #2	$218.91	9.770%	$240.2975	$240.30	$240.30	$240.30
Purchase #3	$227.77	7.810%	$245.5588	$245.56	$245.55	$245.60
Purchase #4	$186.85	6.639%	$199.255	$199.26	$199.25	$199.30
Purchase #5	$9.93	9.701%	$10.8933	$10.89	$10.90	$10.90
Purchase #6	$97.98	7.336%	$105.1678	$105.17	$105.15	$105.20
Purchase #7	$129.33	11.788%	$144.5754	$144.58	$144.60	$144.60
7 purchase totals =	$978.66		$1,059.2848	$1,059.30	$1,059.30	$1,059.40