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	$39.31	5.737%	$41.5652	$41.57	$41.55	$41.60
Purchase #2	$143.79	6.352%	$152.9235	$152.92	$152.90	$152.90
Purchase #3	$52.93	12.271%	$59.425	$59.43	$59.45	$59.40
Purchase #4	$96.87	13.782%	$110.2206	$110.22	$110.20	$110.20
Purchase #5	$83.97	8.805%	$91.3636	$91.36	$91.35	$91.40
Purchase #6	$174.94	4.392%	$182.6234	$182.62	$182.60	$182.60
Purchase #7	$130.34	3.471%	$134.8641	$134.86	$134.85	$134.90
7 purchase totals =	$722.15		$772.9854	$772.98	$772.90	$773.00