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	$81.69	5.716%	$86.3594	$86.36	$86.35	$86.40
Purchase #2	$186.38	7.360%	$200.0976	$200.10	$200.10	$200.10
Purchase #3	$121.92	4.815%	$127.7904	$127.79	$127.80	$127.80
Purchase #4	$240.81	6.860%	$257.3296	$257.33	$257.35	$257.30
Purchase #5	$79.77	4.574%	$83.4187	$83.42	$83.40	$83.40
Purchase #6	$161.47	3.657%	$167.375	$167.38	$167.40	$167.40
Purchase #7	$204.68	13.126%	$231.5463	$231.55	$231.55	$231.50
7 purchase totals =	$1,076.72		$1,153.9170	$1,153.93	$1,153.95	$1,153.90