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	$92.33	13.476%	$104.7724	$104.77	$104.75	$104.80
Purchase #2	$232.31	4.197%	$242.0601	$242.06	$242.05	$242.10
Purchase #3	$196.83	10.408%	$217.3161	$217.32	$217.30	$217.30
Purchase #4	$118.64	10.600%	$131.2158	$131.22	$131.20	$131.20
Purchase #5	$214.32	8.225%	$231.9478	$231.95	$231.95	$231.90
Purchase #6	$35.39	8.779%	$38.4969	$38.50	$38.50	$38.50
Purchase #7	$211.98	10.171%	$233.5405	$233.54	$233.55	$233.50
7 purchase totals =	$1,101.80		$1,199.3496	$1,199.36	$1,199.30	$1,199.30