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	$192.78	9.383%	$210.8685	$210.87	$210.85	$210.90
Purchase #2	$217.59	10.474%	$240.3804	$240.38	$240.40	$240.40
Purchase #3	$134.86	12.853%	$152.1936	$152.19	$152.20	$152.20
Purchase #4	$162.92	5.108%	$171.242	$171.24	$171.25	$171.20
Purchase #5	$207.53	10.216%	$228.7313	$228.73	$228.75	$228.70
Purchase #6	$78.26	5.327%	$82.4289	$82.43	$82.45	$82.40
Purchase #7	$81.47	10.617%	$90.1197	$90.12	$90.10	$90.10
7 purchase totals =	$1,075.41		$1,175.9644	$1,175.96	$1,176.00	$1,175.90