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	$42.41	9.729%	$46.5361	$46.54	$46.55	$46.50
Purchase #2	$210.31	6.329%	$223.6205	$223.62	$223.60	$223.60
Purchase #3	$156.58	5.647%	$165.4221	$165.42	$165.40	$165.40
Purchase #4	$104.70	6.400%	$111.4008	$111.40	$111.40	$111.40
Purchase #5	$27.27	13.299%	$30.8966	$30.90	$30.90	$30.90
Purchase #6	$166.65	13.372%	$188.9344	$188.93	$188.95	$188.90
Purchase #7	$101.93	7.667%	$109.745	$109.75	$109.75	$109.70
7 purchase totals =	$809.85		$876.5555	$876.56	$876.55	$876.40