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	$42.39	12.270%	$47.5913	$47.59	$47.60	$47.60
Purchase #2	$129.37	8.774%	$140.7209	$140.72	$140.70	$140.70
Purchase #3	$67.53	7.181%	$72.3793	$72.38	$72.40	$72.40
Purchase #4	$146.44	13.462%	$166.1538	$166.15	$166.15	$166.20
Purchase #5	$167.47	3.501%	$173.3331	$173.33	$173.35	$173.30
Purchase #6	$233.65	12.686%	$263.2908	$263.29	$263.30	$263.30
Purchase #7	$87.46	4.789%	$91.6485	$91.65	$91.65	$91.60
7 purchase totals =	$874.31		$955.1177	$955.11	$955.15	$955.10