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	$155.54	11.277%	$173.0802	$173.08	$173.10	$173.10
Purchase #2	$47.97	13.537%	$54.4637	$54.46	$54.45	$54.50
Purchase #3	$238.93	13.264%	$270.6217	$270.62	$270.60	$270.60
Purchase #4	$42.66	8.534%	$46.3006	$46.30	$46.30	$46.30
Purchase #5	$200.96	11.188%	$223.4434	$223.44	$223.45	$223.40
Purchase #6	$58.59	4.596%	$61.2828	$61.28	$61.30	$61.30
Purchase #7	$61.88	8.668%	$67.2438	$67.24	$67.25	$67.20
7 purchase totals =	$806.53		$896.4362	$896.42	$896.45	$896.40