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	$126.88	13.764%	$144.3438	$144.34	$144.35	$144.30
Purchase #2	$177.36	12.795%	$200.0532	$200.05	$200.05	$200.10
Purchase #3	$82.84	9.229%	$90.4853	$90.49	$90.50	$90.50
Purchase #4	$244.93	5.535%	$258.4869	$258.49	$258.50	$258.50
Purchase #5	$67.68	8.402%	$73.3665	$73.37	$73.35	$73.40
Purchase #6	$134.27	3.250%	$138.6338	$138.63	$138.65	$138.60
Purchase #7	$96.33	12.361%	$108.2374	$108.24	$108.25	$108.20
7 purchase totals =	$930.29		$1,013.6069	$1,013.61	$1,013.65	$1,013.60