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	$98.43	11.586%	$109.8341	$109.83	$109.85	$109.80
Purchase #2	$82.48	10.386%	$91.0464	$91.05	$91.05	$91.00
Purchase #3	$123.40	4.655%	$129.1443	$129.14	$129.15	$129.10
Purchase #4	$149.74	8.474%	$162.429	$162.43	$162.45	$162.40
Purchase #5	$40.30	4.405%	$42.0752	$42.08	$42.10	$42.10
Purchase #6	$181.84	4.827%	$190.6174	$190.62	$190.60	$190.60
Purchase #7	$44.37	9.495%	$48.5829	$48.58	$48.60	$48.60
7 purchase totals =	$720.56		$773.7293	$773.73	$773.80	$773.60