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	$223.51	11.544%	$249.312	$249.31	$249.30	$249.30
Purchase #2	$104.48	6.608%	$111.384	$111.38	$111.40	$111.40
Purchase #3	$103.41	8.845%	$112.5566	$112.56	$112.55	$112.60
Purchase #4	$213.69	12.816%	$241.0765	$241.08	$241.10	$241.10
Purchase #5	$139.39	5.679%	$147.306	$147.31	$147.30	$147.30
Purchase #6	$73.55	7.337%	$78.9464	$78.95	$78.95	$78.90
Purchase #7	$56.67	7.367%	$60.8449	$60.84	$60.85	$60.80
7 purchase totals =	$914.70		$1,001.4264	$1,001.43	$1,001.45	$1,001.40