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	$180.62	7.720%	$194.5639	$194.56	$194.55	$194.60
Purchase #2	$104.35	4.265%	$108.8005	$108.80	$108.80	$108.80
Purchase #3	$109.76	12.241%	$123.1957	$123.20	$123.20	$123.20
Purchase #4	$137.28	13.112%	$155.2802	$155.28	$155.30	$155.30
Purchase #5	$171.39	11.346%	$190.8359	$190.84	$190.85	$190.80
Purchase #6	$54.98	12.170%	$61.6711	$61.67	$61.65	$61.70
Purchase #7	$136.39	12.564%	$153.526	$153.53	$153.55	$153.50
7 purchase totals =	$894.77		$987.8733	$987.88	$987.90	$987.90