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	$101.57	5.656%	$107.3148	$107.31	$107.30	$107.30
Purchase #2	$144.61	5.261%	$152.2179	$152.22	$152.20	$152.20
Purchase #3	$107.96	10.729%	$119.543	$119.54	$119.55	$119.50
Purchase #4	$115.92	11.165%	$128.8625	$128.86	$128.85	$128.90
Purchase #5	$121.43	7.190%	$130.1608	$130.16	$130.15	$130.20
Purchase #6	$99.64	4.333%	$103.9574	$103.96	$103.95	$104.00
Purchase #7	$63.42	4.855%	$66.499	$66.50	$66.50	$66.50
7 purchase totals =	$754.55		$808.5554	$808.55	$808.50	$808.60