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	$181.26	9.300%	$198.1172	$198.12	$198.10	$198.10
Purchase #2	$82.77	10.773%	$91.6868	$91.69	$91.70	$91.70
Purchase #3	$191.72	13.754%	$218.0892	$218.09	$218.10	$218.10
Purchase #4	$192.72	9.759%	$211.5275	$211.53	$211.55	$211.50
Purchase #5	$53.91	4.853%	$56.5263	$56.53	$56.55	$56.50
Purchase #6	$135.93	12.274%	$152.614	$152.61	$152.60	$152.60
Purchase #7	$106.76	4.638%	$111.7115	$111.71	$111.70	$111.70
7 purchase totals =	$945.07		$1,040.2725	$1,040.28	$1,040.30	$1,040.20