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	$62.69	13.422%	$71.1043	$71.10	$71.10	$71.10
Purchase #2	$104.89	13.767%	$119.3302	$119.33	$119.35	$119.30
Purchase #3	$76.46	7.344%	$82.0752	$82.08	$82.10	$82.10
Purchase #4	$114.50	9.263%	$125.1061	$125.11	$125.10	$125.10
Purchase #5	$213.46	4.301%	$222.6409	$222.64	$222.65	$222.60
Purchase #6	$184.28	11.214%	$204.9452	$204.95	$204.95	$204.90
Purchase #7	$108.48	5.379%	$114.3151	$114.32	$114.30	$114.30
7 purchase totals =	$864.76		$939.5170	$939.53	$939.55	$939.40