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	$99.25	5.711%	$104.9182	$104.92	$104.90	$104.90
Purchase #2	$154.95	6.649%	$165.2526	$165.25	$165.25	$165.30
Purchase #3	$250.68	12.546%	$282.1303	$282.13	$282.15	$282.10
Purchase #4	$38.56	12.165%	$43.2508	$43.25	$43.25	$43.30
Purchase #5	$138.87	9.322%	$151.8155	$151.82	$151.80	$151.80
Purchase #6	$100.46	8.835%	$109.3356	$109.34	$109.35	$109.30
Purchase #7	$138.73	4.755%	$145.3266	$145.33	$145.35	$145.30
7 purchase totals =	$921.50		$1,002.0296	$1,002.04	$1,002.05	$1,002.00