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	$194.91	8.757%	$211.9783	$211.98	$212.00	$212.00
Purchase #2	$155.86	11.415%	$173.6514	$173.65	$173.65	$173.70
Purchase #3	$192.30	13.349%	$217.9701	$217.97	$217.95	$218.00
Purchase #4	$138.98	9.284%	$151.8829	$151.88	$151.90	$151.90
Purchase #5	$57.72	7.243%	$61.9007	$61.90	$61.90	$61.90
Purchase #6	$173.67	6.822%	$185.5178	$185.52	$185.50	$185.50
Purchase #7	$161.41	4.585%	$168.8106	$168.81	$168.80	$168.80
7 purchase totals =	$1,074.85		$1,171.7118	$1,171.71	$1,171.70	$1,171.80