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	$86.36	4.762%	$90.4725	$90.47	$90.45	$90.50
Purchase #2	$173.92	4.505%	$181.7551	$181.76	$181.75	$181.80
Purchase #3	$225.67	7.860%	$243.4077	$243.41	$243.40	$243.40
Purchase #4	$74.27	13.502%	$84.2979	$84.30	$84.30	$84.30
Purchase #5	$139.41	11.572%	$155.5425	$155.54	$155.55	$155.50
Purchase #6	$139.52	4.180%	$145.3519	$145.35	$145.35	$145.40
Purchase #7	$137.37	4.713%	$143.8442	$143.84	$143.85	$143.80
7 purchase totals =	$976.52		$1,044.6718	$1,044.67	$1,044.65	$1,044.70