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	$64.83	11.359%	$72.194	$72.19	$72.20	$72.20
Purchase #2	$39.92	9.313%	$43.6377	$43.64	$43.65	$43.60
Purchase #3	$89.63	6.611%	$95.5554	$95.56	$95.55	$95.60
Purchase #4	$28.71	4.681%	$30.0539	$30.05	$30.05	$30.10
Purchase #5	$158.63	6.356%	$168.7125	$168.71	$168.70	$168.70
Purchase #6	$97.62	8.127%	$105.5536	$105.55	$105.55	$105.60
Purchase #7	$166.30	9.391%	$181.9172	$181.92	$181.90	$181.90
7 purchase totals =	$645.64		$697.6243	$697.62	$697.60	$697.70