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	$141.60	12.774%	$159.688	$159.69	$159.70	$159.70
Purchase #2	$59.33	10.522%	$65.5727	$65.57	$65.55	$65.60
Purchase #3	$99.36	10.225%	$109.5196	$109.52	$109.50	$109.50
Purchase #4	$249.47	8.786%	$271.3884	$271.39	$271.40	$271.40
Purchase #5	$189.37	13.639%	$215.1982	$215.20	$215.20	$215.20
Purchase #6	$72.64	12.520%	$81.7345	$81.73	$81.75	$81.70
Purchase #7	$197.35	5.470%	$208.145	$208.15	$208.15	$208.10
7 purchase totals =	$1,009.12		$1,111.2464	$1,111.25	$1,111.25	$1,111.20