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	$232.59	9.276%	$254.165	$254.17	$254.15	$254.20
Purchase #2	$100.35	11.477%	$111.8672	$111.87	$111.85	$111.90
Purchase #3	$215.32	12.799%	$242.8788	$242.88	$242.90	$242.90
Purchase #4	$87.57	4.535%	$91.5413	$91.54	$91.55	$91.50
Purchase #5	$195.95	3.802%	$203.4	$203.40	$203.40	$203.40
Purchase #6	$69.44	9.296%	$75.8951	$75.90	$75.90	$75.90
Purchase #7	$218.56	10.633%	$241.7995	$241.80	$241.80	$241.80
7 purchase totals =	$1,119.78		$1,221.5469	$1,221.56	$1,221.55	$1,221.60