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	$243.38	13.714%	$276.7571	$276.76	$276.75	$276.80
Purchase #2	$147.73	12.425%	$166.0855	$166.09	$166.10	$166.10
Purchase #3	$249.80	3.723%	$259.1001	$259.10	$259.10	$259.10
Purchase #4	$43.71	4.431%	$45.6468	$45.65	$45.65	$45.60
Purchase #5	$161.98	6.713%	$172.8537	$172.85	$172.85	$172.90
Purchase #6	$167.81	6.339%	$178.4475	$178.45	$178.45	$178.40
Purchase #7	$38.41	12.467%	$43.1986	$43.20	$43.20	$43.20
7 purchase totals =	$1,052.82		$1,142.0893	$1,142.10	$1,142.10	$1,142.10