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	$107.35	3.592%	$111.206	$111.21	$111.20	$111.20
Purchase #2	$144.48	3.421%	$149.4227	$149.42	$149.40	$149.40
Purchase #3	$209.91	11.418%	$233.8775	$233.88	$233.90	$233.90
Purchase #4	$183.41	3.324%	$189.5065	$189.51	$189.50	$189.50
Purchase #5	$63.85	9.829%	$70.1258	$70.13	$70.15	$70.10
Purchase #6	$103.81	5.269%	$109.2797	$109.28	$109.30	$109.30
Purchase #7	$144.49	4.782%	$151.3995	$151.40	$151.40	$151.40
7 purchase totals =	$957.30		$1,014.8177	$1,014.83	$1,014.85	$1,014.80