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	$60.40	4.506%	$63.1216	$63.12	$63.10	$63.10
Purchase #2	$128.82	12.656%	$145.1235	$145.12	$145.10	$145.10
Purchase #3	$229.58	11.694%	$256.4271	$256.43	$256.45	$256.40
Purchase #4	$127.88	11.266%	$142.287	$142.29	$142.30	$142.30
Purchase #5	$78.82	9.469%	$86.2835	$86.28	$86.30	$86.30
Purchase #6	$166.87	10.852%	$184.9787	$184.98	$185.00	$185.00
Purchase #7	$90.67	12.506%	$102.0092	$102.01	$102.00	$102.00
7 purchase totals =	$883.04		$980.2306	$980.23	$980.25	$980.20