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	$43.83	7.579%	$47.1519	$47.15	$47.15	$47.20
Purchase #2	$154.83	6.329%	$164.6292	$164.63	$164.65	$164.60
Purchase #3	$193.53	8.778%	$210.5181	$210.52	$210.50	$210.50
Purchase #4	$220.84	13.274%	$250.1543	$250.15	$250.15	$250.20
Purchase #5	$192.48	8.854%	$209.5222	$209.52	$209.50	$209.50
Purchase #6	$89.28	8.348%	$96.7331	$96.73	$96.75	$96.70
Purchase #7	$144.32	5.745%	$152.6112	$152.61	$152.60	$152.60
7 purchase totals =	$1,039.11		$1,131.3200	$1,131.31	$1,131.30	$1,131.30