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	$39.73	13.371%	$45.0423	$45.04	$45.05	$45.00
Purchase #2	$222.89	8.359%	$241.5214	$241.52	$241.50	$241.50
Purchase #3	$54.90	13.545%	$62.3362	$62.34	$62.35	$62.30
Purchase #4	$162.56	7.584%	$174.8886	$174.89	$174.90	$174.90
Purchase #5	$97.75	3.447%	$101.1194	$101.12	$101.10	$101.10
Purchase #6	$185.70	11.618%	$207.2746	$207.27	$207.25	$207.30
Purchase #7	$228.36	3.139%	$235.5282	$235.53	$235.55	$235.50
7 purchase totals =	$991.89		$1,067.7107	$1,067.71	$1,067.70	$1,067.60