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	$168.77	13.512%	$191.5742	$191.57	$191.55	$191.60
Purchase #2	$167.30	3.766%	$173.6005	$173.60	$173.60	$173.60
Purchase #3	$134.35	6.343%	$142.8718	$142.87	$142.85	$142.90
Purchase #4	$219.32	9.784%	$240.7783	$240.78	$240.80	$240.80
Purchase #5	$237.48	5.213%	$249.8598	$249.86	$249.85	$249.90
Purchase #6	$67.66	7.802%	$72.9388	$72.94	$72.95	$72.90
Purchase #7	$204.70	11.168%	$227.5609	$227.56	$227.55	$227.60
7 purchase totals =	$1,199.58		$1,299.1843	$1,299.18	$1,299.15	$1,299.30