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	$97.49	6.708%	$104.0296	$104.03	$104.05	$104.00
Purchase #2	$201.72	6.118%	$214.0612	$214.06	$214.05	$214.10
Purchase #3	$42.91	3.859%	$44.5659	$44.57	$44.55	$44.60
Purchase #4	$101.89	9.213%	$111.2771	$111.28	$111.30	$111.30
Purchase #5	$100.70	10.235%	$111.0066	$111.01	$111.00	$111.00
Purchase #6	$64.85	13.497%	$73.6028	$73.60	$73.60	$73.60
Purchase #7	$43.36	6.827%	$46.3202	$46.32	$46.30	$46.30
7 purchase totals =	$652.92		$704.8634	$704.87	$704.85	$704.90