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	$170.44	8.415%	$184.7825	$184.78	$184.80	$184.80
Purchase #2	$65.70	3.123%	$67.7518	$67.75	$67.75	$67.80
Purchase #3	$86.40	8.759%	$93.9678	$93.97	$93.95	$94.00
Purchase #4	$201.55	10.554%	$222.8216	$222.82	$222.80	$222.80
Purchase #5	$225.40	13.258%	$255.2835	$255.28	$255.30	$255.30
Purchase #6	$235.91	6.386%	$250.9752	$250.98	$251.00	$251.00
Purchase #7	$56.60	4.826%	$59.3315	$59.33	$59.35	$59.30
7 purchase totals =	$1,042.00		$1,134.9139	$1,134.91	$1,134.95	$1,135.00