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	$231.28	3.686%	$239.805	$239.81	$239.80	$239.80
Purchase #2	$53.29	4.240%	$55.5495	$55.55	$55.55	$55.50
Purchase #3	$120.91	10.229%	$133.2779	$133.28	$133.30	$133.30
Purchase #4	$142.48	6.801%	$152.1701	$152.17	$152.15	$152.20
Purchase #5	$180.47	4.344%	$188.3096	$188.31	$188.30	$188.30
Purchase #6	$120.57	10.164%	$132.8247	$132.82	$132.80	$132.80
Purchase #7	$168.90	7.198%	$181.0574	$181.06	$181.05	$181.10
7 purchase totals =	$1,017.90		$1,082.9942	$1,083.00	$1,082.95	$1,083.00