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	$96.75	7.629%	$104.1311	$104.13	$104.15	$104.10
Purchase #2	$71.25	10.468%	$78.7085	$78.71	$78.70	$78.70
Purchase #3	$71.31	7.852%	$76.9093	$76.91	$76.90	$76.90
Purchase #4	$139.35	10.555%	$154.0584	$154.06	$154.05	$154.10
Purchase #5	$167.77	9.146%	$183.1142	$183.11	$183.10	$183.10
Purchase #6	$64.69	12.681%	$72.8933	$72.89	$72.90	$72.90
Purchase #7	$95.72	8.460%	$103.8179	$103.82	$103.80	$103.80
7 purchase totals =	$706.84		$773.6327	$773.63	$773.60	$773.60