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	$176.83	8.327%	$191.5546	$191.55	$191.55	$191.60
Purchase #2	$32.50	5.443%	$34.269	$34.27	$34.25	$34.30
Purchase #3	$56.70	13.415%	$64.3063	$64.31	$64.30	$64.30
Purchase #4	$82.92	10.379%	$91.5263	$91.53	$91.55	$91.50
Purchase #5	$185.86	5.800%	$196.6399	$196.64	$196.65	$196.60
Purchase #6	$101.36	8.223%	$109.6948	$109.69	$109.70	$109.70
Purchase #7	$240.83	3.523%	$249.3144	$249.31	$249.30	$249.30
7 purchase totals =	$877.00		$937.3053	$937.30	$937.30	$937.30