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	$173.56	3.210%	$179.1313	$179.13	$179.15	$179.10
Purchase #2	$36.59	8.320%	$39.6343	$39.63	$39.65	$39.60
Purchase #3	$168.61	8.241%	$182.5052	$182.51	$182.50	$182.50
Purchase #4	$102.42	8.344%	$110.9659	$110.97	$110.95	$111.00
Purchase #5	$233.61	12.795%	$263.5004	$263.50	$263.50	$263.50
Purchase #6	$218.34	13.791%	$248.4513	$248.45	$248.45	$248.50
Purchase #7	$126.61	12.408%	$142.3198	$142.32	$142.30	$142.30
7 purchase totals =	$1,059.74		$1,166.5082	$1,166.51	$1,166.50	$1,166.50