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	$40.65	12.241%	$45.626	$45.63	$45.65	$45.60
Purchase #2	$159.40	4.150%	$166.0151	$166.02	$166.00	$166.00
Purchase #3	$249.37	10.524%	$275.6137	$275.61	$275.60	$275.60
Purchase #4	$86.98	5.836%	$92.0562	$92.06	$92.05	$92.10
Purchase #5	$107.64	7.636%	$115.8594	$115.86	$115.85	$115.90
Purchase #6	$213.98	6.700%	$228.3167	$228.32	$228.30	$228.30
Purchase #7	$83.25	12.752%	$93.866	$93.87	$93.85	$93.90
7 purchase totals =	$941.27		$1,017.3531	$1,017.37	$1,017.30	$1,017.40