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	$158.77	9.808%	$174.3422	$174.34	$174.35	$174.30
Purchase #2	$52.71	13.646%	$59.9028	$59.90	$59.90	$59.90
Purchase #3	$235.59	4.608%	$246.446	$246.45	$246.45	$246.40
Purchase #4	$207.43	7.524%	$223.037	$223.04	$223.05	$223.00
Purchase #5	$177.88	12.339%	$199.8286	$199.83	$199.85	$199.80
Purchase #6	$81.92	4.397%	$85.522	$85.52	$85.50	$85.50
Purchase #7	$27.98	5.662%	$29.5642	$29.56	$29.55	$29.60
7 purchase totals =	$942.28		$1,018.6428	$1,018.64	$1,018.65	$1,018.50