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	$172.53	4.805%	$180.8201	$180.82	$180.80	$180.80
Purchase #2	$206.67	13.819%	$235.2297	$235.23	$235.25	$235.20
Purchase #3	$39.56	13.517%	$44.9073	$44.91	$44.90	$44.90
Purchase #4	$145.93	3.572%	$151.1426	$151.14	$151.15	$151.10
Purchase #5	$71.85	12.505%	$80.8348	$80.83	$80.85	$80.80
Purchase #6	$234.93	12.566%	$264.4513	$264.45	$264.45	$264.50
Purchase #7	$74.66	11.280%	$83.0816	$83.08	$83.10	$83.10
7 purchase totals =	$946.13		$1,040.4674	$1,040.46	$1,040.50	$1,040.40