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	$66.41	5.675%	$70.1788	$70.18	$70.20	$70.20
Purchase #2	$233.88	3.623%	$242.3535	$242.35	$242.35	$242.40
Purchase #3	$217.49	9.575%	$238.3147	$238.31	$238.30	$238.30
Purchase #4	$119.70	6.434%	$127.4015	$127.40	$127.40	$127.40
Purchase #5	$235.89	9.277%	$257.7735	$257.77	$257.75	$257.80
Purchase #6	$30.96	9.617%	$33.9374	$33.94	$33.95	$33.90
Purchase #7	$153.27	13.623%	$174.15	$174.15	$174.15	$174.20
7 purchase totals =	$1,057.60		$1,144.1094	$1,144.10	$1,144.10	$1,144.20