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	$178.98	9.544%	$196.0619	$196.06	$196.05	$196.10
Purchase #2	$49.34	13.133%	$55.8198	$55.82	$55.80	$55.80
Purchase #3	$88.53	8.768%	$96.2923	$96.29	$96.30	$96.30
Purchase #4	$151.47	9.477%	$165.8248	$165.82	$165.80	$165.80
Purchase #5	$205.54	6.688%	$219.2865	$219.29	$219.30	$219.30
Purchase #6	$231.83	7.642%	$249.5464	$249.55	$249.55	$249.50
Purchase #7	$238.34	5.696%	$251.9158	$251.92	$251.90	$251.90
7 purchase totals =	$1,144.03		$1,234.7475	$1,234.75	$1,234.70	$1,234.70