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	$102.56	9.512%	$112.3155	$112.32	$112.30	$112.30
Purchase #2	$173.81	3.476%	$179.8516	$179.85	$179.85	$179.90
Purchase #3	$159.89	7.288%	$171.5428	$171.54	$171.55	$171.50
Purchase #4	$144.61	6.217%	$153.6004	$153.60	$153.60	$153.60
Purchase #5	$142.86	3.102%	$147.2915	$147.29	$147.30	$147.30
Purchase #6	$224.30	13.363%	$254.2732	$254.27	$254.25	$254.30
Purchase #7	$94.56	7.366%	$101.5253	$101.53	$101.55	$101.50
7 purchase totals =	$1,042.59		$1,120.4003	$1,120.40	$1,120.40	$1,120.40