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	$202.56	5.131%	$212.9534	$212.95	$212.95	$213.00
Purchase #2	$203.80	10.691%	$225.5883	$225.59	$225.60	$225.60
Purchase #3	$93.31	5.494%	$98.4365	$98.44	$98.45	$98.40
Purchase #4	$93.41	3.773%	$96.9344	$96.93	$96.95	$96.90
Purchase #5	$164.84	6.665%	$175.8266	$175.83	$175.85	$175.80
Purchase #6	$102.59	6.415%	$109.1711	$109.17	$109.15	$109.20
Purchase #7	$117.79	11.455%	$131.2828	$131.28	$131.30	$131.30
7 purchase totals =	$978.30		$1,050.1931	$1,050.19	$1,050.25	$1,050.20