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	$100.78	10.474%	$111.3357	$111.34	$111.35	$111.30
Purchase #2	$195.52	11.324%	$217.6607	$217.66	$217.65	$217.70
Purchase #3	$173.38	6.483%	$184.6202	$184.62	$184.60	$184.60
Purchase #4	$32.77	3.502%	$33.9176	$33.92	$33.90	$33.90
Purchase #5	$102.75	3.358%	$106.2003	$106.20	$106.20	$106.20
Purchase #6	$224.38	9.308%	$245.2653	$245.27	$245.25	$245.30
Purchase #7	$134.68	13.177%	$152.4268	$152.43	$152.45	$152.40
7 purchase totals =	$964.26		$1,051.4266	$1,051.44	$1,051.40	$1,051.40