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	$151.62	7.243%	$162.6018	$162.60	$162.60	$162.60
Purchase #2	$96.28	6.266%	$102.3129	$102.31	$102.30	$102.30
Purchase #3	$55.50	11.383%	$61.8176	$61.82	$61.80	$61.80
Purchase #4	$88.98	3.581%	$92.1664	$92.17	$92.15	$92.20
Purchase #5	$37.43	3.735%	$38.828	$38.83	$38.85	$38.80
Purchase #6	$76.62	4.105%	$79.7653	$79.77	$79.75	$79.80
Purchase #7	$183.33	3.851%	$190.39	$190.39	$190.40	$190.40
7 purchase totals =	$689.76		$727.8820	$727.89	$727.85	$727.90