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	$250.61	5.450%	$264.2682	$264.27	$264.25	$264.30
Purchase #2	$102.41	13.818%	$116.561	$116.56	$116.55	$116.60
Purchase #3	$58.45	6.808%	$62.4293	$62.43	$62.45	$62.40
Purchase #4	$189.87	3.522%	$196.5572	$196.56	$196.55	$196.60
Purchase #5	$166.51	13.637%	$189.217	$189.22	$189.20	$189.20
Purchase #6	$75.63	12.704%	$85.238	$85.24	$85.25	$85.20
Purchase #7	$107.30	13.742%	$122.0452	$122.05	$122.05	$122.00
7 purchase totals =	$950.78		$1,036.3159	$1,036.33	$1,036.30	$1,036.30