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	$168.59	6.663%	$179.8232	$179.82	$179.80	$179.80
Purchase #2	$173.66	4.192%	$180.9398	$180.94	$180.95	$180.90
Purchase #3	$145.45	8.740%	$158.1623	$158.16	$158.15	$158.20
Purchase #4	$148.97	6.115%	$158.0795	$158.08	$158.10	$158.10
Purchase #5	$172.48	5.789%	$182.4649	$182.46	$182.45	$182.50
Purchase #6	$158.52	7.412%	$170.2695	$170.27	$170.25	$170.30
Purchase #7	$35.57	4.874%	$37.3037	$37.30	$37.30	$37.30
7 purchase totals =	$1,003.24		$1,067.0429	$1,067.03	$1,067.00	$1,067.10