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	$240.43	11.112%	$267.1466	$267.15	$267.15	$267.10
Purchase #2	$158.66	7.835%	$171.091	$171.09	$171.10	$171.10
Purchase #3	$115.53	7.628%	$124.3426	$124.34	$124.35	$124.30
Purchase #4	$93.49	10.340%	$103.1569	$103.16	$103.15	$103.20
Purchase #5	$54.43	9.311%	$59.498	$59.50	$59.50	$59.50
Purchase #6	$191.59	11.217%	$213.0807	$213.08	$213.10	$213.10
Purchase #7	$152.47	10.277%	$168.1393	$168.14	$168.15	$168.10
7 purchase totals =	$1,006.60		$1,106.4551	$1,106.46	$1,106.50	$1,106.40