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	$133.46	5.674%	$141.0325	$141.03	$141.05	$141.00
Purchase #2	$207.33	13.410%	$235.133	$235.13	$235.15	$235.10
Purchase #3	$106.73	11.492%	$118.9954	$119.00	$119.00	$119.00
Purchase #4	$72.69	10.627%	$80.4148	$80.41	$80.40	$80.40
Purchase #5	$211.51	10.361%	$233.4246	$233.42	$233.40	$233.40
Purchase #6	$43.36	7.859%	$46.7677	$46.77	$46.75	$46.80
Purchase #7	$196.54	13.381%	$222.839	$222.84	$222.85	$222.80
7 purchase totals =	$971.62		$1,078.6070	$1,078.60	$1,078.60	$1,078.50