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	$114.98	6.565%	$122.5284	$122.53	$122.55	$122.50
Purchase #2	$58.78	4.627%	$61.4998	$61.50	$61.50	$61.50
Purchase #3	$121.40	6.553%	$129.3553	$129.36	$129.35	$129.40
Purchase #4	$145.42	4.269%	$151.628	$151.63	$151.65	$151.60
Purchase #5	$89.30	7.254%	$95.7778	$95.78	$95.80	$95.80
Purchase #6	$93.86	7.507%	$100.9061	$100.91	$100.90	$100.90
Purchase #7	$158.29	9.849%	$173.88	$173.88	$173.90	$173.90
7 purchase totals =	$782.03		$835.5754	$835.59	$835.65	$835.60