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	$245.79	9.814%	$269.9118	$269.91	$269.90	$269.90
Purchase #2	$41.87	3.568%	$43.3639	$43.36	$43.35	$43.40
Purchase #3	$234.80	10.750%	$260.041	$260.04	$260.05	$260.00
Purchase #4	$23.78	9.405%	$26.0165	$26.02	$26.00	$26.00
Purchase #5	$96.43	9.362%	$105.4578	$105.46	$105.45	$105.50
Purchase #6	$107.65	5.462%	$113.5298	$113.53	$113.55	$113.50
Purchase #7	$188.37	4.371%	$196.6037	$196.60	$196.60	$196.60
7 purchase totals =	$938.69		$1,014.9245	$1,014.92	$1,014.90	$1,014.90