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	$80.68	13.582%	$91.638	$91.64	$91.65	$91.60
Purchase #2	$249.79	4.651%	$261.4077	$261.41	$261.40	$261.40
Purchase #3	$175.37	6.823%	$187.3355	$187.34	$187.35	$187.30
Purchase #4	$186.53	12.342%	$209.5515	$209.55	$209.55	$209.60
Purchase #5	$62.38	8.282%	$67.5463	$67.55	$67.55	$67.50
Purchase #6	$103.86	7.538%	$111.689	$111.69	$111.70	$111.70
Purchase #7	$122.86	4.783%	$128.7364	$128.74	$128.75	$128.70
7 purchase totals =	$981.47		$1,057.9044	$1,057.92	$1,057.95	$1,057.80