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	$152.93	12.773%	$172.4637	$172.46	$172.45	$172.50
Purchase #2	$167.36	4.387%	$174.7021	$174.70	$174.70	$174.70
Purchase #3	$148.27	7.162%	$158.8891	$158.89	$158.90	$158.90
Purchase #4	$192.91	8.498%	$209.3035	$209.30	$209.30	$209.30
Purchase #5	$46.60	9.666%	$51.1044	$51.10	$51.10	$51.10
Purchase #6	$85.34	12.459%	$95.9725	$95.97	$95.95	$96.00
Purchase #7	$155.91	8.114%	$168.5605	$168.56	$168.55	$168.60
7 purchase totals =	$949.32		$1,030.9958	$1,030.98	$1,030.95	$1,031.10