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	$197.53	10.612%	$218.4919	$218.49	$218.50	$218.50
Purchase #2	$106.57	11.800%	$119.1453	$119.15	$119.15	$119.10
Purchase #3	$80.78	13.346%	$91.5609	$91.56	$91.55	$91.60
Purchase #4	$245.63	10.664%	$271.824	$271.82	$271.80	$271.80
Purchase #5	$152.64	6.141%	$162.0136	$162.01	$162.00	$162.00
Purchase #6	$164.98	10.474%	$182.26	$182.26	$182.25	$182.30
Purchase #7	$133.53	4.183%	$139.1156	$139.12	$139.10	$139.10
7 purchase totals =	$1,081.66		$1,184.4113	$1,184.41	$1,184.35	$1,184.40