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	$213.97	9.746%	$234.8235	$234.82	$234.80	$234.80
Purchase #2	$85.94	11.838%	$96.1136	$96.11	$96.10	$96.10
Purchase #3	$176.72	5.191%	$185.8935	$185.89	$185.90	$185.90
Purchase #4	$157.28	9.272%	$171.863	$171.86	$171.85	$171.90
Purchase #5	$212.44	7.465%	$228.2986	$228.30	$228.30	$228.30
Purchase #6	$196.93	10.832%	$218.2615	$218.26	$218.25	$218.30
Purchase #7	$68.54	5.102%	$72.0369	$72.04	$72.05	$72.00
7 purchase totals =	$1,111.82		$1,207.2906	$1,207.28	$1,207.25	$1,207.30