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	$154.69	11.302%	$172.1731	$172.17	$172.15	$172.20
Purchase #2	$14.33	11.400%	$15.9636	$15.96	$15.95	$16.00
Purchase #3	$159.84	5.314%	$168.3339	$168.33	$168.35	$168.30
Purchase #4	$138.27	7.325%	$148.3983	$148.40	$148.40	$148.40
Purchase #5	$109.28	9.469%	$119.6277	$119.63	$119.65	$119.60
Purchase #6	$119.99	3.155%	$123.7757	$123.78	$123.80	$123.80
Purchase #7	$244.74	9.304%	$267.5106	$267.51	$267.50	$267.50
7 purchase totals =	$941.14		$1,015.7829	$1,015.78	$1,015.80	$1,015.80