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	$159.63	7.171%	$171.0771	$171.08	$171.10	$171.10
Purchase #2	$70.98	12.621%	$79.9384	$79.94	$79.95	$79.90
Purchase #3	$27.89	11.865%	$31.1991	$31.20	$31.20	$31.20
Purchase #4	$97.80	3.142%	$100.8729	$100.87	$100.85	$100.90
Purchase #5	$193.63	11.435%	$215.7716	$215.77	$215.75	$215.80
Purchase #6	$114.38	11.671%	$127.7293	$127.73	$127.75	$127.70
Purchase #7	$43.77	5.333%	$46.1043	$46.10	$46.10	$46.10
7 purchase totals =	$708.08		$772.6927	$772.69	$772.70	$772.70