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	$187.84	11.588%	$209.6069	$209.61	$209.60	$209.60
Purchase #2	$74.55	4.780%	$78.1135	$78.11	$78.10	$78.10
Purchase #3	$114.42	11.375%	$127.4353	$127.44	$127.45	$127.40
Purchase #4	$160.51	5.461%	$169.2755	$169.28	$169.30	$169.30
Purchase #5	$171.98	3.743%	$178.4172	$178.42	$178.40	$178.40
Purchase #6	$5.54	11.813%	$6.1944	$6.19	$6.20	$6.20
Purchase #7	$123.89	12.292%	$139.1186	$139.12	$139.10	$139.10
7 purchase totals =	$838.73		$908.1614	$908.17	$908.15	$908.10