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	$168.69	8.426%	$182.9038	$182.90	$182.90	$182.90
Purchase #2	$36.64	3.474%	$37.9129	$37.91	$37.90	$37.90
Purchase #3	$238.36	6.793%	$254.5518	$254.55	$254.55	$254.60
Purchase #4	$22.30	3.510%	$23.0827	$23.08	$23.10	$23.10
Purchase #5	$6.67	10.412%	$7.3645	$7.36	$7.35	$7.40
Purchase #6	$190.31	3.186%	$196.3733	$196.37	$196.35	$196.40
Purchase #7	$52.46	5.373%	$55.2787	$55.28	$55.30	$55.30
7 purchase totals =	$715.43		$757.4677	$757.45	$757.45	$757.60