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	$43.96	4.442%	$45.9127	$45.91	$45.90	$45.90
Purchase #2	$153.33	13.547%	$174.1016	$174.10	$174.10	$174.10
Purchase #3	$77.49	5.358%	$81.6419	$81.64	$81.65	$81.60
Purchase #4	$8.54	6.464%	$9.092	$9.09	$9.10	$9.10
Purchase #5	$94.27	7.541%	$101.3789	$101.38	$101.40	$101.40
Purchase #6	$91.54	9.304%	$100.0569	$100.06	$100.05	$100.10
Purchase #7	$104.51	12.220%	$117.2811	$117.28	$117.30	$117.30
7 purchase totals =	$573.64		$629.4651	$629.46	$629.50	$629.50