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	$230.44	7.340%	$247.3543	$247.35	$247.35	$247.40
Purchase #2	$219.54	3.182%	$226.5258	$226.53	$226.55	$226.50
Purchase #3	$74.73	5.519%	$78.8543	$78.85	$78.85	$78.90
Purchase #4	$98.91	5.846%	$104.6923	$104.69	$104.70	$104.70
Purchase #5	$72.45	8.346%	$78.4967	$78.50	$78.50	$78.50
Purchase #6	$79.43	8.661%	$86.3094	$86.31	$86.30	$86.30
Purchase #7	$241.28	8.818%	$262.5561	$262.56	$262.55	$262.60
7 purchase totals =	$1,016.78		$1,084.7889	$1,084.79	$1,084.80	$1,084.90