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	$101.43	7.695%	$109.235	$109.24	$109.25	$109.20
Purchase #2	$150.49	11.701%	$168.0988	$168.10	$168.10	$168.10
Purchase #3	$112.34	13.147%	$127.1093	$127.11	$127.10	$127.10
Purchase #4	$143.43	5.269%	$150.9873	$150.99	$151.00	$151.00
Purchase #5	$92.86	12.834%	$104.7777	$104.78	$104.80	$104.80
Purchase #6	$245.64	3.427%	$254.0581	$254.06	$254.05	$254.10
Purchase #7	$122.40	6.667%	$130.5604	$130.56	$130.55	$130.60
7 purchase totals =	$968.59		$1,044.8266	$1,044.84	$1,044.85	$1,044.90