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	$168.94	13.444%	$191.6523	$191.65	$191.65	$191.70
Purchase #2	$135.27	13.802%	$153.94	$153.94	$153.95	$153.90
Purchase #3	$205.49	8.398%	$222.7471	$222.75	$222.75	$222.70
Purchase #4	$20.32	6.736%	$21.6888	$21.69	$21.70	$21.70
Purchase #5	$209.74	4.365%	$218.8952	$218.90	$218.90	$218.90
Purchase #6	$49.53	13.495%	$56.2141	$56.21	$56.20	$56.20
Purchase #7	$211.27	4.529%	$220.8384	$220.84	$220.85	$220.80
7 purchase totals =	$1,000.56		$1,085.9759	$1,085.98	$1,086.00	$1,085.90