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	$148.85	10.656%	$164.7115	$164.71	$164.70	$164.70
Purchase #2	$245.36	10.872%	$272.0355	$272.04	$272.05	$272.00
Purchase #3	$238.75	10.801%	$264.5374	$264.54	$264.55	$264.50
Purchase #4	$97.30	8.467%	$105.5384	$105.54	$105.55	$105.50
Purchase #5	$159.48	4.594%	$166.8065	$166.81	$166.80	$166.80
Purchase #6	$104.82	3.253%	$108.2298	$108.23	$108.25	$108.20
Purchase #7	$26.57	9.801%	$29.1741	$29.17	$29.15	$29.20
7 purchase totals =	$1,021.13		$1,111.0332	$1,111.04	$1,111.05	$1,110.90