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	$85.89	5.744%	$90.8235	$90.82	$90.80	$90.80
Purchase #2	$57.87	5.654%	$61.142	$61.14	$61.15	$61.10
Purchase #3	$151.79	3.488%	$157.0844	$157.08	$157.10	$157.10
Purchase #4	$93.66	9.736%	$102.7787	$102.78	$102.80	$102.80
Purchase #5	$172.49	3.539%	$178.5944	$178.59	$178.60	$178.60
Purchase #6	$193.58	6.823%	$206.788	$206.79	$206.80	$206.80
Purchase #7	$222.84	9.279%	$243.5173	$243.52	$243.50	$243.50
7 purchase totals =	$978.12		$1,040.7283	$1,040.72	$1,040.75	$1,040.70