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	$179.55	10.542%	$198.4782	$198.48	$198.50	$198.50
Purchase #2	$98.43	5.209%	$103.5572	$103.56	$103.55	$103.60
Purchase #3	$211.59	12.400%	$237.8272	$237.83	$237.85	$237.80
Purchase #4	$118.64	10.225%	$130.7709	$130.77	$130.75	$130.80
Purchase #5	$247.87	11.355%	$276.0156	$276.02	$276.00	$276.00
Purchase #6	$142.75	9.438%	$156.2227	$156.22	$156.20	$156.20
Purchase #7	$79.34	4.369%	$82.8064	$82.81	$82.80	$82.80
7 purchase totals =	$1,078.17		$1,185.6782	$1,185.69	$1,185.65	$1,185.70