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	$167.72	12.585%	$188.8276	$188.83	$188.85	$188.80
Purchase #2	$215.76	11.171%	$239.8625	$239.86	$239.85	$239.90
Purchase #3	$211.41	9.159%	$230.773	$230.77	$230.75	$230.80
Purchase #4	$221.43	4.649%	$231.7243	$231.72	$231.70	$231.70
Purchase #5	$119.47	6.840%	$127.6417	$127.64	$127.65	$127.60
Purchase #6	$74.61	7.360%	$80.1013	$80.10	$80.10	$80.10
Purchase #7	$41.94	7.690%	$45.1652	$45.17	$45.15	$45.20
7 purchase totals =	$1,052.34		$1,144.0956	$1,144.09	$1,144.05	$1,144.10