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	$51.51	5.366%	$54.274	$54.27	$54.25	$54.30
Purchase #2	$6.75	11.711%	$7.5405	$7.54	$7.55	$7.50
Purchase #3	$113.56	10.546%	$125.536	$125.54	$125.55	$125.50
Purchase #4	$107.93	3.135%	$111.3136	$111.31	$111.30	$111.30
Purchase #5	$56.86	9.537%	$62.2827	$62.28	$62.30	$62.30
Purchase #6	$110.86	3.466%	$114.7024	$114.70	$114.70	$114.70
Purchase #7	$137.47	9.805%	$150.9489	$150.95	$150.95	$150.90
7 purchase totals =	$584.94		$626.5981	$626.59	$626.60	$626.50