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	$38.98	3.369%	$40.2932	$40.29	$40.30	$40.30
Purchase #2	$214.51	10.390%	$236.7976	$236.80	$236.80	$236.80
Purchase #3	$213.70	9.655%	$234.3327	$234.33	$234.35	$234.30
Purchase #4	$106.68	3.374%	$110.2794	$110.28	$110.30	$110.30
Purchase #5	$242.32	10.309%	$267.3008	$267.30	$267.30	$267.30
Purchase #6	$96.28	4.390%	$100.5067	$100.51	$100.50	$100.50
Purchase #7	$191.70	4.795%	$200.892	$200.89	$200.90	$200.90
7 purchase totals =	$1,104.17		$1,190.4024	$1,190.40	$1,190.45	$1,190.40