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	$215.42	6.117%	$228.5972	$228.60	$228.60	$228.60
Purchase #2	$34.98	7.466%	$37.5916	$37.59	$37.60	$37.60
Purchase #3	$199.33	7.202%	$213.6857	$213.69	$213.70	$213.70
Purchase #4	$156.31	12.790%	$176.302	$176.30	$176.30	$176.30
Purchase #5	$188.83	9.666%	$207.0823	$207.08	$207.10	$207.10
Purchase #6	$35.57	4.139%	$37.0422	$37.04	$37.05	$37.00
Purchase #7	$173.73	13.259%	$196.7649	$196.76	$196.75	$196.80
7 purchase totals =	$1,004.17		$1,097.0659	$1,097.06	$1,097.10	$1,097.10