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	$247.90	4.479%	$259.0034	$259.00	$259.00	$259.00
Purchase #2	$159.42	4.579%	$166.7198	$166.72	$166.70	$166.70
Purchase #3	$167.73	13.376%	$190.1656	$190.17	$190.15	$190.20
Purchase #4	$162.32	3.268%	$167.6246	$167.62	$167.60	$167.60
Purchase #5	$39.32	10.311%	$43.3743	$43.37	$43.35	$43.40
Purchase #6	$162.43	5.146%	$170.7886	$170.79	$170.80	$170.80
Purchase #7	$232.47	4.797%	$243.6216	$243.62	$243.60	$243.60
7 purchase totals =	$1,171.59		$1,241.2979	$1,241.29	$1,241.20	$1,241.30