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	$155.84	13.701%	$177.1916	$177.19	$177.20	$177.20
Purchase #2	$70.97	13.590%	$80.6148	$80.61	$80.60	$80.60
Purchase #3	$69.76	4.330%	$72.7806	$72.78	$72.80	$72.80
Purchase #4	$145.85	7.557%	$156.8719	$156.87	$156.85	$156.90
Purchase #5	$119.56	6.794%	$127.6829	$127.68	$127.70	$127.70
Purchase #6	$84.69	6.104%	$89.8595	$89.86	$89.85	$89.90
Purchase #7	$120.89	5.114%	$127.0723	$127.07	$127.05	$127.10
7 purchase totals =	$767.56		$832.0736	$832.06	$832.05	$832.20