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	$220.33	3.750%	$228.5924	$228.59	$228.60	$228.60
Purchase #2	$223.39	4.574%	$233.6079	$233.61	$233.60	$233.60
Purchase #3	$81.62	10.144%	$89.8995	$89.90	$89.90	$89.90
Purchase #4	$65.83	10.340%	$72.6368	$72.64	$72.65	$72.60
Purchase #5	$90.95	5.432%	$95.8904	$95.89	$95.90	$95.90
Purchase #6	$75.58	8.524%	$82.0224	$82.02	$82.00	$82.00
Purchase #7	$223.75	7.590%	$240.7326	$240.73	$240.75	$240.70
7 purchase totals =	$981.45		$1,043.3820	$1,043.38	$1,043.40	$1,043.30