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	$235.71	3.468%	$243.8844	$243.88	$243.90	$243.90
Purchase #2	$178.52	4.342%	$186.2713	$186.27	$186.25	$186.30
Purchase #3	$149.34	7.510%	$160.5554	$160.56	$160.55	$160.60
Purchase #4	$166.91	11.773%	$186.5603	$186.56	$186.55	$186.60
Purchase #5	$187.26	10.777%	$207.441	$207.44	$207.45	$207.40
Purchase #6	$54.41	9.336%	$59.4897	$59.49	$59.50	$59.50
Purchase #7	$39.93	4.862%	$41.8714	$41.87	$41.85	$41.90
7 purchase totals =	$1,012.08		$1,086.0735	$1,086.07	$1,086.05	$1,086.20