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	$188.88	5.237%	$198.7716	$198.77	$198.75	$198.80
Purchase #2	$113.63	12.482%	$127.8133	$127.81	$127.80	$127.80
Purchase #3	$64.27	12.479%	$72.2903	$72.29	$72.30	$72.30
Purchase #4	$181.82	3.159%	$187.5637	$187.56	$187.55	$187.60
Purchase #5	$181.44	11.607%	$202.4997	$202.50	$202.50	$202.50
Purchase #6	$123.58	9.153%	$134.8913	$134.89	$134.90	$134.90
Purchase #7	$231.43	5.539%	$244.2489	$244.25	$244.25	$244.20
7 purchase totals =	$1,085.05		$1,168.0788	$1,168.07	$1,168.05	$1,168.10