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	$69.54	5.752%	$73.5399	$73.54	$73.55	$73.50
Purchase #2	$234.39	3.834%	$243.3765	$243.38	$243.40	$243.40
Purchase #3	$65.63	3.340%	$67.822	$67.82	$67.80	$67.80
Purchase #4	$156.59	9.210%	$171.0119	$171.01	$171.00	$171.00
Purchase #5	$67.77	6.496%	$72.1723	$72.17	$72.15	$72.20
Purchase #6	$78.29	12.475%	$88.0567	$88.06	$88.05	$88.10
Purchase #7	$198.92	5.709%	$210.2763	$210.28	$210.30	$210.30
7 purchase totals =	$871.13		$926.2556	$926.26	$926.25	$926.30