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	$84.70	5.148%	$89.0604	$89.06	$89.05	$89.10
Purchase #2	$162.57	5.568%	$171.6219	$171.62	$171.60	$171.60
Purchase #3	$139.80	13.417%	$158.557	$158.56	$158.55	$158.60
Purchase #4	$93.48	7.409%	$100.4059	$100.41	$100.40	$100.40
Purchase #5	$92.67	4.329%	$96.6817	$96.68	$96.70	$96.70
Purchase #6	$66.87	5.342%	$70.4422	$70.44	$70.45	$70.40
Purchase #7	$204.70	9.699%	$224.5539	$224.55	$224.55	$224.60
7 purchase totals =	$844.79		$911.3230	$911.32	$911.30	$911.40