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	$90.27	7.315%	$96.8733	$96.87	$96.85	$96.90
Purchase #2	$62.75	7.639%	$67.5435	$67.54	$67.55	$67.50
Purchase #3	$242.34	13.413%	$274.8451	$274.85	$274.85	$274.80
Purchase #4	$177.28	12.200%	$198.9082	$198.91	$198.90	$198.90
Purchase #5	$185.67	4.113%	$193.3066	$193.31	$193.30	$193.30
Purchase #6	$109.28	4.262%	$113.9375	$113.94	$113.95	$113.90
Purchase #7	$129.98	7.249%	$139.4023	$139.40	$139.40	$139.40
7 purchase totals =	$997.57		$1,084.8165	$1,084.82	$1,084.80	$1,084.70