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	$92.76	7.548%	$99.7615	$99.76	$99.75	$99.80
Purchase #2	$140.68	7.170%	$150.7668	$150.77	$150.75	$150.80
Purchase #3	$138.44	8.589%	$150.3306	$150.33	$150.35	$150.30
Purchase #4	$100.98	4.172%	$105.1929	$105.19	$105.20	$105.20
Purchase #5	$200.69	13.195%	$227.171	$227.17	$227.15	$227.20
Purchase #6	$162.62	13.353%	$184.3346	$184.33	$184.35	$184.30
Purchase #7	$119.32	6.657%	$127.2631	$127.26	$127.25	$127.30
7 purchase totals =	$955.49		$1,044.8205	$1,044.81	$1,044.80	$1,044.90