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	$21.76	3.152%	$22.4459	$22.45	$22.45	$22.40
Purchase #2	$115.65	13.736%	$131.5357	$131.54	$131.55	$131.50
Purchase #3	$92.27	6.465%	$98.2353	$98.24	$98.25	$98.20
Purchase #4	$219.59	11.378%	$244.575	$244.58	$244.60	$244.60
Purchase #5	$232.28	3.400%	$240.1775	$240.18	$240.20	$240.20
Purchase #6	$189.76	5.656%	$200.4928	$200.49	$200.50	$200.50
Purchase #7	$167.82	4.217%	$174.897	$174.90	$174.90	$174.90
7 purchase totals =	$1,039.13		$1,112.3592	$1,112.38	$1,112.45	$1,112.30