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	$181.59	9.530%	$198.8955	$198.90	$198.90	$198.90
Purchase #2	$203.71	12.594%	$229.3652	$229.37	$229.35	$229.40
Purchase #3	$249.76	5.493%	$263.4793	$263.48	$263.50	$263.50
Purchase #4	$95.98	3.711%	$99.5418	$99.54	$99.55	$99.50
Purchase #5	$61.98	8.232%	$67.0822	$67.08	$67.10	$67.10
Purchase #6	$156.30	9.711%	$171.4783	$171.48	$171.50	$171.50
Purchase #7	$112.48	4.394%	$117.4224	$117.42	$117.40	$117.40
7 purchase totals =	$1,061.80		$1,147.2647	$1,147.27	$1,147.30	$1,147.30