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	$172.28	4.416%	$179.8879	$179.89	$179.90	$179.90
Purchase #2	$100.37	3.657%	$104.0405	$104.04	$104.05	$104.00
Purchase #3	$101.41	6.555%	$108.0574	$108.06	$108.05	$108.10
Purchase #4	$19.54	4.495%	$20.4183	$20.42	$20.40	$20.40
Purchase #5	$89.58	7.518%	$96.3146	$96.31	$96.30	$96.30
Purchase #6	$126.31	8.311%	$136.8076	$136.81	$136.80	$136.80
Purchase #7	$102.97	6.541%	$109.7053	$109.71	$109.70	$109.70
7 purchase totals =	$712.46		$755.2316	$755.24	$755.20	$755.20