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	$117.81	8.263%	$127.5446	$127.54	$127.55	$127.50
Purchase #2	$91.72	11.398%	$102.1742	$102.17	$102.15	$102.20
Purchase #3	$98.92	6.583%	$105.4319	$105.43	$105.45	$105.40
Purchase #4	$233.47	7.835%	$251.7624	$251.76	$251.75	$251.80
Purchase #5	$240.91	12.507%	$271.0406	$271.04	$271.05	$271.00
Purchase #6	$54.76	5.146%	$57.5779	$57.58	$57.60	$57.60
Purchase #7	$211.36	10.337%	$233.2083	$233.21	$233.20	$233.20
7 purchase totals =	$1,048.95		$1,148.7399	$1,148.73	$1,148.75	$1,148.70