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	$110.56	7.655%	$119.0234	$119.02	$119.00	$119.00
Purchase #2	$90.33	7.228%	$96.8591	$96.86	$96.85	$96.90
Purchase #3	$119.76	3.168%	$123.554	$123.55	$123.55	$123.60
Purchase #4	$136.95	3.852%	$142.2253	$142.23	$142.25	$142.20
Purchase #5	$92.60	8.521%	$100.4904	$100.49	$100.50	$100.50
Purchase #6	$43.52	8.292%	$47.1287	$47.13	$47.15	$47.10
Purchase #7	$243.91	7.562%	$262.3545	$262.35	$262.35	$262.40
7 purchase totals =	$837.63		$891.6354	$891.63	$891.65	$891.70