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	$207.29	4.821%	$217.2835	$217.28	$217.30	$217.30
Purchase #2	$110.71	13.729%	$125.9094	$125.91	$125.90	$125.90
Purchase #3	$5.54	10.605%	$6.1275	$6.13	$6.15	$6.10
Purchase #4	$104.95	6.618%	$111.8956	$111.90	$111.90	$111.90
Purchase #5	$128.96	4.573%	$134.8573	$134.86	$134.85	$134.90
Purchase #6	$41.67	5.856%	$44.1102	$44.11	$44.10	$44.10
Purchase #7	$114.77	11.185%	$127.607	$127.61	$127.60	$127.60
7 purchase totals =	$713.89		$767.7905	$767.80	$767.80	$767.80